ww: put test result trailers on a new line

docs/build-system.md

@@ -7047,6 +7047,149 @@ transaction, stage, workdir, and generated-file cleanup. Existing signal,
 timeout, interruption, concurrent-driver, and public-output transaction owners
 cover the unchanged mechanisms at those boundaries.
 
+### 11.33 Implemented newline before directory test result trailers
+
+When a directory-owned test product has emitted a nonempty combined capture
+whose final byte is not newline, `ww test` now emits exactly one newline before
+its existing `ok` or run-status `FAIL` trailer. Empty and already
+newline-terminated captures gain no byte. The rule belongs only to the
+coordinator boundary between completed test-process output and its result
+trailer; it does not rewrite the capture or affect a route with no coordinator
+trailer.
+
+#### Pinned Go evidence and classification
+
+The sole authority is official Go 1.26.5 at commit
+`c19862e5f8415b4f24b189d065ed739517c548ba`:
+
+- `(*runTestActor).Act` selects one output writer/buffer for a package test
+  ([`cmd/go/internal/test/test.go`, lines 1436–1499](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/go/internal/test/test.go#L1436-L1499)),
+  then assigns that same writer to the test command's stdout and stderr and
+  retains the resulting bytes as `out`
+  ([lines 1661–1708](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/go/internal/test/test.go#L1661-L1708)).
+- On success, a nonempty `out` without a trailing newline receives one before
+  the `ok` record
+  ([lines 1712–1732](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/go/internal/test/test.go#L1712-L1732)).
+  On failure with partial output, the same check inserts one before `FAIL`
+  ([lines 1733–1769](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/go/internal/test/test.go#L1733-L1769)).
+- Official `test_fail_newline.txt` asserts that buffered partial failure output
+  and `FAIL` begin on different lines, and that buffered verbose partial
+  success output and `ok` begin on different lines. It also records the
+  deliberate streaming-mode exception
+  ([lines 3–35](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/go/testdata/script/test_fail_newline.txt#L3-L35)).
+
+Those source rules and official script assertions are behavior directly
+implemented or asserted by pinned Go. Applying the buffered-package boundary
+to WW's directory-product capture is derived from that implementation: WW's
+manifest-free directory coordinator likewise owns the completed combined bytes
+and immediately appends a package result trailer. Excluding raw single-file
+tests and later manual execution of retained binaries is also derived from the
+pinned distinction: those WW routes have no coordinator-owned `ok` or `FAIL`
+trailer to separate.
+
+#### Fresh four-axis audit and direct pre-fix measurements
+
+The bounded audit considered all four permanent axes and selected only this
+test-output gap:
+
+- **Go-like build:** pinned `(*ErrorReporter).errorUnresolved` gives an
+  undeclared main function its dedicated link error
+  ([`cmd/link/internal/ld/errors.go`, lines 29–65](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/link/internal/ld/errors.go#L29-L65)).
+  `TestUndefinedRelocErrors` directly requires build failure and that message
+  ([`cmd/link/internal/ld/ld_test.go`, lines 19–45](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/link/internal/ld/ld_test.go#L19-L45)),
+  using official `issue10978/main.go`, whose main function is absent
+  ([lines 5–27](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/link/internal/ld/testdata/issue10978/main.go#L5-L27)).
+  Direct Cstage and WWstage `ww build -o /dev/null` probes of a selected WW
+  command package without `main` both exited `1`, produced the identical
+  `w6l: undefined reference to 'main'` then `ww: w6l failed` diagnostics, and
+  published nothing. This candidate was aligned.
+- **Go-like test:** a selected external `*_test.ww` initializer wrote exactly
+  `partial-success` without newline and exited `0`. Both stages exited `0`,
+  wrote no stderr, and emitted 72 stdout bytes beginning
+  `partial-successok   `. The corresponding initializer wrote exactly
+  `partial-failure` to stderr and exited `7`; both commands exited `1`, wrote
+  no coordinator stderr, and emitted 86 stdout bytes beginning
+  `partial-failureFAIL `. Full Cstage and WWstage captures were byte-identical.
+  These are directly measured pre-fix WW facts and establish the selected
+  externally observable difference.
+- **Go-like package:** `MultiplePackageError` represents conflicting selected
+  package clauses and formats the two declarations
+  ([`go/build/build.go`, lines 538–548](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/go/build/build.go#L538-L548));
+  the scanner creates it when selected files disagree
+  ([lines 930–967](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/go/build/build.go#L930-L967)),
+  and `TestMultiplePackageImport` asserts the typed result and files
+  ([`go/build/build_test.go`, lines 105–124](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/go/build/build_test.go#L105-L124)).
+  Direct WW directories declaring `alpha` and `beta` were rejected before any
+  producer by both stages with the same positioned conflict diagnostic. This
+  candidate was aligned.
+- **Go-like import:** `loadImport` rejects a package declared `main` when it is
+  imported from another directory
+  ([`cmd/go/internal/load/pkg.go`, lines 787–805](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/go/internal/load/pkg.go#L787-L805));
+  official `import_main.txt` asserts the rule for builds and internal/external
+  tests
+  ([lines 3–35](https://github.com/golang/go/blob/c19862e5f8415b4f24b189d065ed739517c548ba/src/cmd/go/testdata/script/import_main.txt#L3-L35)).
+  Both WW stages rejected a direct dotted import of a package declared `main`
+  with the identical `ww: package cmdpkg is a program, not an importable
+  package` diagnostic. This candidate was aligned.
+
+The direct Go source and official-test statements above are behavior directly
+implemented or asserted by pinned Go. The WW command results are directly
+measured behavior. The conclusion that the selected change is a runtime
+presentation boundary, with no build, package, or import identity effect, is
+derived from the pinned placement after command completion and before the
+result record.
+
+#### Ownership, final behavior, and preserved boundaries
+
+`internal/wwpackage.pkgemitgroup` is the true owner because it alone has both
+the completed product-local combined capture and knowledge that an existing
+directory result trailer follows. It first emits the capture unchanged, then
+emits one separator only when the capture is nonempty and its last byte is not
+newline, then follows the established success or failure branch. The check is
+shared by Cstage and WWstage and is independent for every canonically ordered
+product, including internal, external, and combined variants; dependency
+initialization; filters and list mode; concurrent products; and the private run
+of a retained request.
+
+Empty output does not acquire a leading blank line, and output already ending
+in newline does not acquire a second one. A nonzero exit or signal retains its
+existing process classification and `FAIL` text; only a preceding partial line
+is terminated. Test-harness timeout and ordinary assertion output already end
+in newline and therefore remain byte-identical. A child that cannot start has
+no completed capture/trailer boundary in this function. Parent interruption,
+producer failure, and load, compile, assemble, archive, link, or install
+failure retain their existing diagnostics and precedence. Raw single-file
+tests and later direct execution of retained binaries have no package
+coordinator result trailer and retain their exact process bytes.
+
+Loading, graph construction, action construction and scheduling, compiler,
+assembler, archiver, linker, generated main, test executable, and retained
+artifact bytes are unchanged. The separator is emitted after the private
+process completes; it is not written into the capture, executable, interface,
+archive, work record, or public destination. Running retention remains private
+build, private run, then guarded install. Failed, signalled, interrupted, or
+unstartable runs still publish nothing and preserve prior retained bytes.
+Concurrent products retain separate capture files and canonical emission;
+there is no shared mutable newline state. Existing process-group cleanup,
+transaction rollback, temporary-root removal, and staged-file cleanup are
+unchanged.
+
+Physical source directories remain runtime/loader metadata only and do not
+become package, import, graph, action, artifact, symbol, `.wwi`, publication,
+or persistence identity. No persisted byte or key changes, so build workdir
+format remains `18`, test workdir format remains `19`, and semantic storage
+format remains `3`.
+
+The WW-native `directory_test_trailer_starts_on_new_line` observer proves both
+stages for unterminated stdout success, unterminated stderr failure,
+unterminated signal output, already terminated output, and empty output. It
+also covers concurrent products, a filter, list mode, running retained
+publication, retained executable byte identity, and the unchanged raw/manual
+routes; complete stdout and stderr from the concurrent Cstage and WWstage runs
+must match exactly. Existing package execution, timeout, interruption,
+transaction, persistence, byte-identity, and cleanup owners continue to prove
+the mechanisms this slice does not alter.
+
 ## 12. Candidate architectures and hard-gate decision
 
 Five candidates were developed as coherent systems, not as feature bins.