wcc,ww: flip driver to separate-compilation only; delete build_one amalgamator (M4 E3-C1, #22)

build_one_sep (per-package compile + .wwi interfaces + link) becomes the
sole build path. do_build/do_run/do_test and the ww twins all route
through it; --sep is now an accepted no-op and the run-rejects-sep guard
is removed.

Deleted the single-file amalgamator, both stages: build_one, expand,
expand_dir, peek_package (+ the wwstage twins + strictpkgmismatch).
unit_has_package is retained -- the sep scan loop's inline-package check
needs it. The sep-shared helpers (enumerate_dir_ww, locate_import*,
import_path_form, ImportSet, and ww counterparts) stay; they back the
surviving sep path.

Restores missing-package enforcement under sep by construction: the sep
scan loop loudly rejects an unresolvable import (cannot find package
<name>) unless the package is defined inline in the same unit -- matching
the deleted amalgamator and closing the silent-accept the flip would
otherwise introduce.

All 5 wwstage tools relink (each is built via the now-sep `ww build`);
emitted asm is byte-identical to the combined build per bootstrap input,
so the binary md5 delta is pure link layout, not codegen.

selfhost/cmd/ww/main.combined.ww is now stale and unregenerable (its
writer build_one is deleted); #90 deletes it next.

Test retargets folded in (rule-11 carve-out, #61/#133 precedent): each
asserts post-flip-only behavior, is un-pre-migratable unlike #93/#94/#103,
and splitting reddens one side. Closes #97.
- 989_slttypepref -> dir-package layout (xb imports xa so both same-leaf
  `invalid` types are in scope at xb.f); inline-multipackage was the
  amalgamator shape, deleted with the flip.
- 989_sepbuild_run -> run --sep now genuinely runs (exit 7), not the old
  loud-reject (exit 2); + a private per-pid WW_PKGCACHE so the cs/ww
  per-package byte-id compare on the shared real lib pkgs (rt/time/os) no
  longer races concurrent siblings on the global out/.pkgcache (the flip
  made sep the sole path, so every test now contends that cache).
- 737_direnum -> the deleted strictpkgmismatch "differs from" wording ->
  sep's "does not match import path" (shared substring, wwstage terser #68).
- 989_lib_byteid -> corpus-completeness scan excludes generated .sepwork
  scratch (the old `! -name '*.combined.ww'` exclude didn't cover the new
  sep artifact).

test/wcc/737_direnum.c

@@ -88,8 +88,12 @@ main(void)
 		(void)tmp;
 	}
 
-	/* bad: mismatched package decls in same dir → strict-same-package
-	 * error. Both stages must surface "differs from" in stderr. */
+	/* bad: mismatched package decls in same dir → import-path mismatch
+	 * error. E3-C1: the amalgamator's strict-same-package "differs from"
+	 * check is deleted; under sep w6c rejects the composed unit with
+	 * "package <p> does not match import path <i>" (wwstage is terser per
+	 * #68, so match the shared "does not match import path" substring).
+	 * Both stages must surface it in stderr. */
 	{
 		const char *src = "test/wcc/data/direnum/bad_entry.ww";
 		snprintf(errp, sizeof errp, "/tmp/direnum_%d_bad.err", getpid());
@@ -102,8 +106,8 @@ main(void)
 		if (rc == 0) {
 			fprintf(stderr, "737[bad-cstage]: expected build failure, succeeded\n");
 			fail++;
-		} else if (!stderr_contains(errp, "differs from")) {
-			fprintf(stderr, "737[bad-cstage]: stderr missing 'differs from'\n");
+		} else if (!stderr_contains(errp, "does not match import path")) {
+			fprintf(stderr, "737[bad-cstage]: stderr missing 'does not match import path'\n");
 			fail++;
 		}
 		unlink(errp);
@@ -116,8 +120,8 @@ main(void)
 			if (rc == 0) {
 				fprintf(stderr, "737[bad-wwstage]: expected build failure, succeeded\n");
 				fail++;
-			} else if (!stderr_contains(errp, "differs from")) {
-				fprintf(stderr, "737[bad-wwstage]: stderr missing 'differs from'\n");
+			} else if (!stderr_contains(errp, "does not match import path")) {
+				fprintf(stderr, "737[bad-wwstage]: stderr missing 'does not match import path'\n");
 				fail++;
 			}
 			unlink(errp);
@@ -129,7 +133,7 @@ main(void)
 	 * (#16): the old 2048-capped peek missed that decl, so the strict-
 	 * same-package check skipped the file and the mismatch went
 	 * undetected (build wrongly succeeded); the whole-file peek finds it
-	 * → "differs from". Both stages. (reviewer-batcha pin.) */
+	 * → "does not match import path". Both stages. (reviewer-batcha pin.) */
 	{
 		const char *src = "test/wcc/data/direnum/bad_deep_entry.ww";
 		snprintf(errp, sizeof errp, "/tmp/direnum_%d_baddeep.err", getpid());
@@ -142,8 +146,8 @@ main(void)
 		if (rc == 0) {
 			fprintf(stderr, "737[bad-deep-cstage]: expected build failure, succeeded\n");
 			fail++;
-		} else if (!stderr_contains(errp, "differs from")) {
-			fprintf(stderr, "737[bad-deep-cstage]: stderr missing 'differs from'\n");
+		} else if (!stderr_contains(errp, "does not match import path")) {
+			fprintf(stderr, "737[bad-deep-cstage]: stderr missing 'does not match import path'\n");
 			fail++;
 		}
 		unlink(errp);
@@ -156,8 +160,8 @@ main(void)
 			if (rc == 0) {
 				fprintf(stderr, "737[bad-deep-wwstage]: expected build failure, succeeded\n");
 				fail++;
-			} else if (!stderr_contains(errp, "differs from")) {
-				fprintf(stderr, "737[bad-deep-wwstage]: stderr missing 'differs from'\n");
+			} else if (!stderr_contains(errp, "does not match import path")) {
+				fprintf(stderr, "737[bad-deep-wwstage]: stderr missing 'does not match import path'\n");
 				fail++;
 			}
 			unlink(errp);

test/wcc/989_lib_byteid.c

@@ -421,8 +421,12 @@ static int
 corpus_complete(const char *cwd)
 {
 	char cmd[2048];
+	/* E3-C1: the flip routes lib @test builds through sep, which drops
+	 * <stem>.sepwork/<pkg>.unit.ww scratch next to source; exclude it so
+	 * the scan enrols real source dirs only, not generated work dirs. */
 	snprintf(cmd, sizeof cmd, "cd %s && find lib -name '*.ww' "
-	    "! -name '*.combined.ww' | sed 's|/[^/]*$||' | sort -u", cwd);
+	    "! -name '*.combined.ww' ! -path '*.sepwork/*' "
+	    "| sed 's|/[^/]*$||' | sort -u", cwd);
 	FILE *p = popen(cmd, "r");
 	if (!p) return -1;
 	char dir[512];

test/wcc/989_sepbuild_run.c

@@ -236,6 +236,18 @@ main(void)
 	runwait(cmd);
 	mkdir(td, 0755);
 
+	/* E3-C1: with the flip making sep the sole build path, every concurrent
+	 * test now writes the global out/.pkgcache; this test's cs/ww per-package
+	 * byte-id compare on the heavily-shared real lib pkgs (rt/time/os) then
+	 * races a sibling building the same pkg. Pin a private per-pid cache so
+	 * the cs and ww legs are isolated (system() builds inherit this env).
+	 * pkgcache writes are non-atomic (cp -f), the real torn-read bug; this
+	 * hermetic isolation is correct standalone, pending #104 (atomic
+	 * temp+rename, both stages). */
+	char cachedir[80];
+	snprintf(cachedir, sizeof cachedir, "%s/pkgcache", td);
+	setenv("WW_PKGCACHE", cachedir, 1);
+
 	char rootww[1024];
 	snprintf(rootww, sizeof rootww, "%s/root.ww", td);
 	if (write_file(rootww, root_src)) { fail++; goto out; }
@@ -339,13 +351,11 @@ main(void)
 		}
 	}
 
-	/* run --sep symmetry (#46 c3): `run` has no sep-compile-then-run
-	 * path (out of commit-3 scope), so BOTH stages must LOUD-REJECT
-	 * `run --sep` identically (rule 10) — not one silently ignore it.
-	 * The reject exits 2 (the driver's usage/flag-error code); assert
-	 * cs and ww agree AND actually rejected (exit 2, not a build+run
-	 * that happened to exit nonzero). This row is the gate-visible
-	 * guard whose absence let the divergence hide. */
+	/* run --sep symmetry: E3-C1 makes sep the sole compile path, so
+	 * `run` now genuinely sep-compiles-then-runs (the old "no sep run
+	 * path → loud-reject exit 2" is gone with the amalgamator). BOTH
+	 * stages must build+run the cross-boundary fixture identically
+	 * (rule 10) and exit EXPECT_EXIT — `--sep` is an accepted no-op. */
 	{
 		int rc_cs, rc_ww;
 		snprintf(cmd, sizeof cmd,
@@ -354,9 +364,10 @@ main(void)
 		snprintf(cmd, sizeof cmd,
 		    "%s/ww_ww run --sep %s >/dev/null 2>&1", bin, rootww);
 		rc_ww = runwait(cmd);
-		if (rc_cs != rc_ww || rc_cs != 2) {
+		if (rc_cs != rc_ww || rc_cs != EXPECT_EXIT) {
 			fprintf(stderr, "sepbuild FAIL: run --sep cs=%d ww=%d "
-			    "(both must loud-reject, exit 2)\n", rc_cs, rc_ww);
+			    "(both must run via sep, exit %d)\n", rc_cs, rc_ww,
+			    EXPECT_EXIT);
 			fail++;
 		}
 	}

test/wcc/989_slttypepref_run.c

@@ -26,14 +26,19 @@
  * The shadow row was RED pre-c1 (ww resolved xa's !i8 -> exit 1, the wrong
  * module's type under rc=0). The noshadow control pins the non-shadow path
  * (scopelookupprefer lands on the SK_TYPE directly) so the fix can't
- * perturb it. Single-file multi-package source is the sanctioned shape
- * (cmd/ww/main.c).
+ * perturb it.
+ *
+ * E3-C1 retarget: the single-file multi-package source the original used
+ * is the amalgamator shape, deleted with the flip (ww is now strictly
+ * dir=module). Re-expressed as a dir-package tree: xb/ and xa/ both export
+ * `type invalid`, and xb IMPORTS xa so both `invalid` leaves are in scope
+ * during xb's sep-compile — the exact two-module same-leaf collision the
+ * scopelookuptype mod-preference fix governs. A regression flips to xa's
+ * !i8 -> exit 1.
  */
 #include <stdio.h>
 #include <stdlib.h>
-#include <string.h>
 #include <unistd.h>
-#include <sys/stat.h>
 #include <sys/wait.h>
 
 static int
@@ -45,62 +50,70 @@ runwait(const char *cmd)
 	return -1;
 }
 
-struct row { const char *label; const char *src; int want_exit; };
+/* Only xb's param name varies between rows; xa and the root are shared.
+ * `xb_param` is the parameter spelling: "invalid" shadows the type leaf,
+ * "x" does not. */
+struct row { const char *label; const char *xb_param; int want_exit; };
 
 static const struct row rows[] = {
-	{ "shadow",
-	  "package xb;\n"
-	  "export type invalid = !i64;\n"
-	  "export fn f(invalid: i32) i64 = { return size(invalid): i64; };\n"
-	  "package xa;\n"
-	  "export type invalid = !i8;\n"
-	  "package main;\n"
-	  "import xb;\n"
-	  "import xa;\n"
-	  "fn main() int = { return xb.f(0): int; };\n",
-	  8 },
-
-	{ "noshadow",
-	  "package xb;\n"
-	  "export type invalid = !i64;\n"
-	  "export fn f(x: i32) i64 = { return size(invalid): i64; };\n"
-	  "package xa;\n"
-	  "export type invalid = !i8;\n"
-	  "package main;\n"
-	  "import xb;\n"
-	  "import xa;\n"
-	  "fn main() int = { return xb.f(0): int; };\n",
-	  8 },
+	{ "shadow",   "invalid", 8 },
+	{ "noshadow", "x",       8 },
 };
 
+static int
+write_file(const char *path, const char *content)
+{
+	FILE *f = fopen(path, "wb");
+	if (!f) return -1;
+	fputs(content, f);
+	fclose(f);
+	return 0;
+}
+
 static int
 run_build(const char *driver, const struct row *r, int i)
 {
-	char src[64], tmpdir[64], cmd[1024];
-	snprintf(src, sizeof src, "/tmp/sltp_%d_%d.ww", getpid(), i);
-	snprintf(tmpdir, sizeof tmpdir, "/tmp/sltp_%d_d_%d", getpid(), i);
+	char dir[64], sub[128], path[256], xbsrc[512], cmd[1024];
+	snprintf(dir, sizeof dir, "/tmp/sltp_%d_d_%d", getpid(), i);
 
-	FILE *f = fopen(src, "wb");
-	if (!f) return -2;
-	fputs(r->src, f);
-	fclose(f);
+	snprintf(cmd, sizeof cmd, "rm -rf %s && mkdir -p %s/xa %s/xb",
+	    dir, dir, dir);
+	if (runwait(cmd) != 0) return -2;
 
-	mkdir(tmpdir, 0755);
-	snprintf(cmd, sizeof cmd, "cd %s && %s build %s 2>/dev/null",
-	    tmpdir, driver, src);
+	snprintf(path, sizeof path, "%s/xa/xa.ww", dir);
+	if (write_file(path, "package xa;\nexport type invalid = !i8;\n"))
+		return -2;
+
+	snprintf(sub, sizeof sub, "%s/xb/xb.ww", dir);
+	snprintf(xbsrc, sizeof xbsrc,
+	    "package xb;\n"
+	    "import xa;\n"
+	    "export type invalid = !i64;\n"
+	    "export fn f(%s: i32) i64 = { return size(invalid): i64; };\n",
+	    r->xb_param);
+	if (write_file(sub, xbsrc)) return -2;
+
+	snprintf(path, sizeof path, "%s/root.ww", dir);
+	if (write_file(path,
+	    "package main;\n"
+	    "import xb;\n"
+	    "import xa;\n"
+	    "fn main() int = { return xb.f(0): int; };\n"))
+		return -2;
+
+	/* canonical dir-package build: cd into the package root, build the
+	 * root unit; the binary lands in cwd (#22 dir=module). */
+	snprintf(cmd, sizeof cmd, "cd %s && %s build root.ww 2>/dev/null",
+	    dir, driver);
 	int brc = runwait(cmd);
 
-	const char *base = strrchr(src, '/');
-	base = base ? base + 1 : src;
 	char outbin[128];
-	snprintf(outbin, sizeof outbin, "%s/%s", tmpdir, base);
-	char *dot = strrchr(outbin, '.');
-	if (dot && strcmp(dot, ".ww") == 0) *dot = '\0';
-
+	snprintf(outbin, sizeof outbin, "%s/root", dir);
 	int got = -1;
 	if (brc == 0) got = runwait(outbin);
 
-	unlink(src); unlink(outbin); rmdir(tmpdir);
+	snprintf(cmd, sizeof cmd, "rm -rf %s", dir);
+	runwait(cmd);
 	return brc == 0 ? got : -1;
 }