fix: ignore hidden named source operands

docs/test-system-v2.md

@@ -219,6 +219,26 @@ every `-j` level, and `-j 1` — the default — matches the former sequential
 run loop exactly. Measured on the 31-package `lib/...` walk:
 7.0s sequential, 2.4s at `-j 4`.
 
+The raw single-source compatibility route applies package-source eligibility
+before it invokes the compiler or harness. An existing operand ending `.ww`
+whose final requested basename begins `.` or `_` is ignored exactly as it is by
+directory discovery, even when the name also ends `_test.ww`; the file is not
+opened and cannot contribute a test descriptor, package declaration, import,
+variant, graph action, diagnostic, artifact, retained binary, or persistent
+state. A normal explicit running request exits 1 with exact `FAIL\n` stdout and
+the driver's `directory contains no WW package sources` stderr; `-c` and `-S`
+omit the final marker. Visible wrong-platform raw names remain eligible, and
+only the requested basename matters for symlinks (including non-regular
+targets) and hidden parent directories.
+CLI/target and the existing raw package-option shape retain precedence. Cold
+rejection creates no work or temporary product; warm rejection preserves prior
+work and public bytes without transaction residue. The focused
+`named_source_prefixes_are_ignored` package observer proves these rules in both
+driver stages, including malformed/import precedence, prefix-before-test and
+platform classification, symlink spelling, output rollback, residue, and
+diagnostic/artifact parity. Directory package coordination and test process,
+filter, timeout, signal, and descendant topology are unchanged.
+
 List mode uses that same product process and initialization boundary but starts
 no per-test child. The shared language harness emits only selected qualified
 test names, one per line in descriptor order. A valid filter selecting no tests