lib: migrate every test file to the canonical *_test.ww name

25 renames (git mv, content untouched). _test.ww is what the package
coordinator's test detection and the sep loader's canonical exclusion
key on; the old *test.ww spellings survived only through the
line-leading-@test compatibility scan. Consumers updated in place:
LIBRARY_TESTS, the libbyteid roster, the 901/974/975/976 carriers that
copy or invoke these files, and the check.c/check.ww + path/ftos
comments that cite them. Closes the open-driver-work migration bullet.

test/wcc/901_asserttyped_gap.c

@@ -151,7 +151,7 @@ main(void)
 		  "B fn-ptr struct-field call", 0, 1 },
 		{ "lib/encoding/utf8/utf8.ww",
 		  "C abort intrinsic callee", 0, 1 },
-		{ "lib/fnmatch/fnmatchtest.ww",
+		{ "lib/fnmatch/fnmatch_test.ww",
 		  "D module-leaf == type/fn name", 0, 1 },
 		{ "lib/math/random/random_test.ww",
 		  "D module-leaf == type/fn name", 0, 1 },

test/wcc/974_getenv_run.c

@@ -2,13 +2,13 @@
  * 974_getenv_run — execute the lib/os getenv smoke fixture under the
  * C-side `ww run` driver and assert exit 0.
  *
- * Pre-arranges the environment that lib/os/ostest.ww asserts against:
+ * Pre-arranges the environment that lib/os/os_test.ww asserts against:
  *
  *   WW_TEST_GETENV   = "hello-world"   (set, non-empty)
  *   WW_TEST_EMPTY    = ""              (set, empty value)
  *   WW_TEST_NOT_SET  unset             (unsetenv-cleared)
  *
- * The child `ww run` process inherits this env, so ostest.ww's
+ * The child `ww run` process inherits this env, so os_test.ww's
  * `os.getenv` calls see exactly the state we configured here. This
  * is the "C-side env arrangement" pattern (parent sets, child reads)
  * — proper POSIX shape for stdlib testing without a `setenv` ww
@@ -46,12 +46,12 @@ main(void)
 	char cwd[1024];
 	if (getcwd(cwd, sizeof cwd) == NULL) return 1;
 
-	/* Pre-arrange the env state ostest.ww asserts against. */
+	/* Pre-arrange the env state os_test.ww asserts against. */
 	setenv("WW_TEST_GETENV", "hello-world", 1);
 	setenv("WW_TEST_EMPTY", "", 1);
 	unsetenv("WW_TEST_NOT_SET");
 
-	const char *src = "lib/os/ostest.ww";
+	const char *src = "lib/os/os_test.ww";
 	char path[1024], cmd[2048];
 	snprintf(path, sizeof path, "%s/%s", cwd, src);
 	snprintf(cmd, sizeof cmd, "%s/ww test %s", bin, path);

test/wcc/975_dirs_run.c

@@ -5,9 +5,9 @@
  * Workflow:
  *   1. mkdtemp /tmp/wwdirs-XXXXXX  — fresh per run, no cross-run
  *      stale state, no parallel-test conflicts.
- *   2. setenv the four cohort env states (see lib/dirs/dirstest.ww
+ *   2. setenv the four cohort env states (see lib/dirs/dirs_test.ww
  *      file header for the contract).
- *   3. exec `ww test lib/dirs/dirstest.ww`. The fixture reads
+ *   3. exec `ww test lib/dirs/dirs_test.ww`. The fixture reads
  *      WW_TEST_TMPDIR + the XDG_/HOME envs and asserts.
  *   4. Remove the exact auto-created child dirs bottom-up, then the
  *      mkdtemp-owned root.
@@ -63,7 +63,7 @@ main(void)
 	unsetenv("XDG_STATE_HOME");
 	setenv("WW_TEST_TMPDIR", tmpl, 1);
 
-	const char *src = "lib/dirs/dirstest.ww";
+	const char *src = "lib/dirs/dirs_test.ww";
 	char path[1024], cmd[2048];
 	snprintf(path, sizeof path, "%s/%s", cwd, src);
 	snprintf(cmd, sizeof cmd, "%s/ww test %s", bin, path);

test/wcc/976_stat_run.c

@@ -10,9 +10,9 @@
  *        <tmp>/symlink   →  ./regfile  (relative symlink)
  *        <tmp>/subdir       directory, mode 0700
  *   3. setenv WW_TEST_STAT_REGFILE / SYMLINK / SUBDIR / NOENT with
- *      the absolute paths; lib/os/stattest.ww reads them via
+ *      the absolute paths; lib/os/stat_test.ww reads them via
  *      os.getenv and exercises stat/lstat/fstat/exists.
- *   4. exec `ww test lib/os/stattest.ww`.
+ *   4. exec `ww test lib/os/stat_test.ww`.
  *   5. Remove the exact children and then the mkdtemp-owned root.
  *
  * Same wrapper shape as 970-975; cleanup runs on success and failure.
@@ -62,7 +62,7 @@ main(void)
 	snprintf(symlink_path, sizeof symlink_path, "%s/symlink", tmpl);
 	snprintf(subdir, sizeof subdir, "%s/subdir", tmpl);
 	snprintf(noent, sizeof noent, "%s/does-not-exist", tmpl);
-	const char *src = "lib/os/stattest.ww";
+	const char *src = "lib/os/stat_test.ww";
 	int fail = 0, subdir_owned = 0;
 
 	/* Populate. */