lib/strings+test: Hare port (dup/concat/trim/index/contains/has{pre,suf}fix/compare/utf8)

Hare-faithful index/predicate family per ref/hare/strings/{dup,
concat,trim,index,suffix,contains,compare,utf8}.ha. Non-variadic
subset (concat 2-arg, trim single-rune, contains single-needle)
pending task #16 — cstage variadic-pack drops .len on multi-field
element types; ship the Hare-faithful single-arg shape now, file
the variadic upgrade as follow-up. `sub` follow-up filed as #29
(commit 2 with iterator + utf8.chars relocation).

Surface: dup, concat, trim/trimprefix/trimsuffix (single rune),
hasprefix, hassuffix (both with (str|rune) sum needle),
byteindex, rbyteindex (both with (str|rune) sum needle),
contains (single str needle), compare, toutf8, fromutf8_unsafe,
runebytes helper. (str|rune) match arms route the rune via
utf8.encoderune into a [4]u8 scratch then bytes.index/rindex —
drew-devault's directive for clean Hare-fidelity over invented
ASCII-only rune-byte arms.

byteindex / rbyteindex rune-arm semantic correction —
corpus-coverage-blind unmask. Pre-existing impl scanned for
`r: u8` (broken for all rune values >0x7F since strings.ww first
landed; no caller exercised it). Replaced with utf8.encoderune-
based scan via runebytes helper. Severity-marker: silent
wrong-result for any non-ASCII rune needle, masked by zero
in-tree callers until lib/strings + utf8 chain pulled the shape
in.

Build-system propagation: lib/strings depends transitively on
lib/encoding/utf8 (via byteindex's rune arm). cmd/ww driver's
locate_import_in (cmd/ww/main.c:85) walks `<dir>/<name>.ww` and
`<dir>/<name>/<name>.ww` only — `use utf8;` doesn't find
lib/encoding/utf8/utf8.ww without explicit `-I lib/encoding/utf8`.
Propagated through 5 wwstage-tool Makefile targets + 7 test
wrappers + test/wcc/995_self_rebuild.c sprintf lines. Task #17
filed for the principled resolver fix (subdir walk vs Hare's
qualified `use encoding::utf8;` notation).

This commit chain (#15 strings) surfaced 7 cgen bugs during
landing: #16 cstage variadic-pack, #17 resolver nested-paths,
#27 aliaslookup leaf-collision, #22 zero-init !void/void-alias
let-decl, #15-cstage retscr SSoT name, #24 composite CALL return
as composite arg, #28 N_DOT calleeparams. All blocking ones
fixed (#16/#17 deferred-with-stopgap, others fixed in their
respective commits). Pre-flight + stop-and-surface discipline
held throughout — no workarounds shipped in stdlib.

Tests:
  - 966_strings_run drives lib/strings/stringstest.ww via ww run.
    15 @test fns: dup (alloc, multibyte), concat (empty, lopsided,
    multibyte), trim/ltrim/rtrim incl. 4-byte rune U+1D68A,
    hasprefix/hassuffix with (str|rune) incl. multibyte,
    byteindex/rbyteindex both arms 1/2/3/4-byte rune coverage,
    compare. Cited from ref/hare/strings/+test.ha where vectors
    apply.

100/100 ok. 995_self_rebuild stays green (ww2==ww3==ww4 byte-id).

test/wcc/700_e2e.c

@@ -1748,8 +1748,14 @@ main(void)
 		char tmpdir[64];
 		snprintf(tmpdir, sizeof tmpdir, "/tmp/wwe2e_%d_d_%d", getpid(), i);
 		mkdir(tmpdir, 0755);
-		snprintf(cmd, sizeof cmd, "cd %s && %s/ww build %s",
-		    tmpdir, bin, src);
+		/* -I lib/encoding/utf8 for any fixture that pulls in fmt /
+		 * strconv / strings via `use` (transitive utf8.encoderune;
+		 * task #17). Unused -I is benign for fixtures that don't. */
+		char cwd700[1024];
+		if (getcwd(cwd700, sizeof cwd700) == NULL) { fail++; continue; }
+		snprintf(cmd, sizeof cmd,
+		    "cd %s && %s/ww build -I %s/lib/encoding/utf8 %s",
+		    tmpdir, bin, cwd700, src);
 		if (runwait(cmd) != 0) { fail++; continue; }
 
 		char outbin[128];

test/wcc/966_strings_run.c

@@ -0,0 +1,55 @@
+/*
+ * 966_strings_run — execute the lib/strings @test fixture under the
+ * C-side `ww run` driver and assert exit 0.
+ *
+ * Same thin-wrapper shape as 967_bytes_run / 968_utf8_run / 979_hex_run:
+ * stringstest.ww carries its own `export fn main()` that drives the
+ * @test fns and signals which case failed via the exit code.
+ *
+ * -I lib/encoding/utf8 is required because lib/strings.byteindex
+ * encodes the rune-needle arm via utf8.encoderune; the import resolver
+ * doesn't yet walk encoding/ subdirs (task #17).
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+static int
+runwait(const char *cmd)
+{
+	int rc = system(cmd);
+	if (rc == -1) return -1;
+	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
+	return 1;
+}
+
+int
+main(void)
+{
+	const char *bin = getenv("BIN");
+	if (!bin) bin = "out/bin";
+	char absbin[1024];
+	if (bin[0] != '/') {
+		char cwd[1024];
+		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
+		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
+		bin = absbin;
+	}
+	char cwd[1024];
+	if (getcwd(cwd, sizeof cwd) == NULL) return 1;
+
+	const char *src = "lib/strings/stringstest.ww";
+	char path[1024], cmd[2048];
+	snprintf(path, sizeof path, "%s/%s", cwd, src);
+	snprintf(cmd, sizeof cmd,
+	    "%s/ww run -I %s/lib/encoding/utf8 %s",
+	    bin, cwd, path);
+	int rc = runwait(cmd);
+	if (rc != 0) {
+		fprintf(stderr, "strings_run FAIL: %s exited %d\n", src, rc);
+		return 1;
+	}
+	printf("strings_run: %s ok\n", src);
+	return 0;
+}

test/wcc/970_fmt_run.c

@@ -41,7 +41,9 @@ main(void)
 	const char *src = "lib/fmt/fmttest.ww";
 	char path[1024], cmd[2048];
 	snprintf(path, sizeof path, "%s/%s", cwd, src);
-	snprintf(cmd, sizeof cmd, "%s/ww run %s", bin, path);
+	/* -I lib/encoding/utf8 — task #17 */
+	snprintf(cmd, sizeof cmd,
+	    "%s/ww run -I %s/lib/encoding/utf8 %s", bin, cwd, path);
 	int rc = runwait(cmd);
 	if (rc != 0) {
 		fprintf(stderr, "fmt_run FAIL: %s exited %d\n", src, rc);

test/wcc/971_log_run.c

@@ -41,7 +41,9 @@ main(void)
 	const char *src = "lib/log/logtest.ww";
 	char path[1024], cmd[2048];
 	snprintf(path, sizeof path, "%s/%s", cwd, src);
-	snprintf(cmd, sizeof cmd, "%s/ww run %s", bin, path);
+	/* -I lib/encoding/utf8 — task #17 */
+	snprintf(cmd, sizeof cmd,
+	    "%s/ww run -I %s/lib/encoding/utf8 %s", bin, cwd, path);
 	int rc = runwait(cmd);
 	if (rc != 0) {
 		fprintf(stderr, "log_run FAIL: %s exited %d\n", src, rc);

test/wcc/972_fnmatch_run.c

@@ -41,7 +41,9 @@ main(void)
 	const char *src = "lib/fnmatch/fnmatchtest.ww";
 	char path[1024], cmd[2048];
 	snprintf(path, sizeof path, "%s/%s", cwd, src);
-	snprintf(cmd, sizeof cmd, "%s/ww run %s", bin, path);
+	/* -I lib/encoding/utf8 — task #17 */
+	snprintf(cmd, sizeof cmd,
+	    "%s/ww run -I %s/lib/encoding/utf8 %s", bin, cwd, path);
 	int rc = runwait(cmd);
 	if (rc != 0) {
 		fprintf(stderr, "fnmatch_run FAIL: %s exited %d\n", src, rc);

test/wcc/982_getopt_run.c

@@ -40,7 +40,10 @@ main(void)
 	const char *src = "lib/getopt/getopttest.ww";
 	char path[1024], cmd[2048];
 	snprintf(path, sizeof path, "%s/%s", cwd, src);
-	snprintf(cmd, sizeof cmd, "%s/ww run %s", bin, path);
+	/* -I lib/encoding/utf8: getopt -> strings -> utf8.encoderune
+	 * (task #17 — resolver doesn't yet walk encoding/ subdirs). */
+	snprintf(cmd, sizeof cmd,
+	    "%s/ww run -I %s/lib/encoding/utf8 %s", bin, cwd, path);
 	int rc = runwait(cmd);
 	if (rc != 0) {
 		fprintf(stderr, "getopt_run FAIL: %s exited %d\n", src, rc);

test/wcc/990_selfhost.c

@@ -99,9 +99,11 @@ probe_smoke(const char *bin)
 	snprintf(tmpdir, sizeof tmpdir, "/tmp/wwsh_%d", getpid());
 	mkdir(tmpdir, 0755);
 	char cmd[2048];
+	/* -I lib/encoding/utf8: smoke.ww uses strconv -> strings ->
+	 * utf8.encoderune (task #17 — resolver doesn't walk encoding/). */
 	snprintf(cmd, sizeof cmd,
-	    "cd %s && %s/ww build %s/selfhost/test/smoke.ww >/dev/null 2>&1",
-	    tmpdir, bin, cwd);
+	    "cd %s && %s/ww build -I %s/lib/encoding/utf8 %s/selfhost/test/smoke.ww >/dev/null 2>&1",
+	    tmpdir, bin, cwd, cwd);
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "smoke FAIL: ww build did not succeed\n");
 		return -1;
@@ -743,8 +745,8 @@ probe_ww_links(const char *bin)
 		runwait(cmd);
 		/* ww build to get the .combined.ww as a side effect. */
 		snprintf(cmd, sizeof cmd,
-		    "cd %s && %s/ww build -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/selfhost/cmd/wcc %s >/dev/null 2>&1",
-		    tmpdir, bin, cwd, cwd, cwd, cwd, tmpsrc);
+		    "cd %s && %s/ww build -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/lib/encoding/utf8 -I %s/selfhost/cmd/wcc %s >/dev/null 2>&1",
+		    tmpdir, bin, cwd, cwd, cwd, cwd, cwd, tmpsrc);
 		if (runwait(cmd) != 0) {
 			fprintf(stderr, "ww-links FAIL: ww build %s\n", fix);
 			fail++;

test/wcc/993_ww_ww.c

@@ -150,8 +150,8 @@ main(void)
 	static char wwdump_src[2048], wwdump_incs[4096];
 	snprintf(wwdump_src,  sizeof wwdump_src,  "%s/selfhost/cmd/wwdump/main.ww", cwd);
 	snprintf(wwdump_incs, sizeof wwdump_incs,
-	    "%s/lib/ww:%s/lib/ww/lex:%s/lib/ww/parse:%s/selfhost/cmd/wcc",
-	    cwd, cwd, cwd, cwd);
+	    "%s/lib/ww:%s/lib/ww/lex:%s/lib/ww/parse:%s/lib/encoding/utf8:%s/selfhost/cmd/wcc",
+	    cwd, cwd, cwd, cwd, cwd);
 	cases[1].src  = wwdump_src;
 	cases[1].incs = wwdump_incs;
 

test/wcc/995_self_rebuild.c

@@ -62,6 +62,9 @@ slurp_eq(const char *a, const char *b)
 /* Each tool builds via `ww_ww build -I <local> -I lib/ww -I selfhost/cmd/wcc src`.
  * lib/ww holds the language introspection (lex/tok/ast/parse/typ/sym);
  * selfhost/cmd/wcc holds the compiler internals (mem/check/cgen*).
+ * lib/encoding/utf8 carries the rune codec strings.byteindex needs;
+ * the import resolver doesn't yet walk encoding/ subdirs (task #17),
+ * so the dep travels as an explicit -I until it does.
  * Some tools have a local module dir (w6a, w6l with sibling .ww files).
  * inc_local is "" for tools without one (w6c, ww, wwdump).
  */
@@ -77,14 +80,14 @@ rebuild_one(const char *bin, const char *cwd, const char *tool,
 
 	if (inc_local && inc_local[0]) {
 		snprintf(cmd, sizeof cmd,
-		    "cd %s && %s/ww_ww build -I %s/%s -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/selfhost/cmd/wcc "
+		    "cd %s && %s/ww_ww build -I %s/%s -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/lib/encoding/utf8 -I %s/selfhost/cmd/wcc "
 		    "%s/%s >/dev/null 2>&1",
-		    workdir, bin, cwd, inc_local, cwd, cwd, cwd, cwd, cwd, src_rel);
+		    workdir, bin, cwd, inc_local, cwd, cwd, cwd, cwd, cwd, cwd, src_rel);
 	} else {
 		snprintf(cmd, sizeof cmd,
-		    "cd %s && %s/ww_ww build -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/selfhost/cmd/wcc "
+		    "cd %s && %s/ww_ww build -I %s/lib/ww -I %s/lib/ww/lex -I %s/lib/ww/parse -I %s/lib/encoding/utf8 -I %s/selfhost/cmd/wcc "
 		    "%s/%s >/dev/null 2>&1",
-		    workdir, bin, cwd, cwd, cwd, cwd, cwd, src_rel);
+		    workdir, bin, cwd, cwd, cwd, cwd, cwd, cwd, src_rel);
 	}
 	if (runwait(cmd) != 0) {
 		fprintf(stderr, "self-rebuild FAIL: ww_ww build errored on %s\n", tool);