feat(#1733): normalize-path-in-content production AST rule + fix Windows agent-skills content leak (Phase 5) (#1736)

* feat(#1733): normalize-path-in-content production AST rule (Phase 5)

ADR-1703 Phase 5 — the first production-code rule. local/normalize-path-in-content
(src/**/*.cts, @typescript-eslint/parser): flags a path-returning fn result
(path.basename excluded — returns a separator-less filename) interpolated into an
@-reference / config-dir markdown body without .replace(/\\/g,'/') normalization,
per RULESET.CONTENT-PATH-NORMALIZATION / DEFECT.WINDOWS-PATH-LEAK-IN-MARKDOWN-CONTENT.

Build-and-assess found the canonical defect site (computePathPrefix) already
compliant and only 1 src/ hit — a false positive (path.basename in a status
message) — eliminated by narrowing (exclude basename; require a real @-ref/
config-dir marker, not bare .md). 0 src/ violations: clean forward-prevention.

The out-of-band disable-ban now scans src/**/*.cts too (typescript-estree) so the
production rule also cannot be eslint-disabled. Registered (error) + PROTECTED_RULES;
CONTEXT.md predicates + how-to doc updated.

- RuleTester suite (26 cases)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* docs(#1733): add changeset for Windows agent-skills path-leak fix

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix: harden mutation-matrix.cjs stdin read against EAGAIN on non-blocking pipe

scripts/mutation-matrix.cjs read piped stdin via readFileSync(process.stdin.fd).
On macOS libuv marks the stdin pipe fd non-blocking, so a synchronous read can
throw EAGAIN before the writer fills the pipe — intermittently, under heavy CI
shard load — aborting the script (status 2) and flaking mutation-matrix-ratchet.
Replace with readStdinSync(): an fs.readSync loop that retries on EAGAIN (1ms
synchronous Atomics.wait yield), stops on 0-byte/EOF, and rethrows other errors.
Deterministic regression test injects EAGAIN via an fs.readSync monkeypatch.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* ci: re-run golden-install-parity on src/lib + installer changes (close drift guard)

golden-install-parity hashes every installed bin/lib/*.cjs per runtime, so it
must re-run whenever the built lib could change. ci-test-scope selected it for
neither src/** nor installer changes, so a source-only edit (e.g. #1691's
milestone.cts/roadmap.cts) recompiled bin/lib and silently drifted the golden
fixtures past the scoped lane. Add golden-install-parity.test.cjs to both the
'TS runtime sources' and 'installer and package layout' selection rules, with
behavioral regression tests for each.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: review-bot <review-bot@gsd>

src/init.cts

@@ -2183,7 +2183,7 @@ function buildAgentSkillsBlock(
     if (entry.kind === 'directive') {
       return `- Load the \`${entry.name}\` skill via the Skill tool before proceeding (plugin-provided).`;
     }
-    return `- @${entry.ref}`;
+    return `- @${String(entry.ref).replace(/\\/g, '/')}`;
   }).join('\n');
   return `<agent_skills>\nRead these user-configured skills:\n${lines}\n</agent_skills>`;
 }