feat(#1740): require-fs-op-fallback production AST rule + Windows transient-lock retry (Phase 6) (#1742)

* feat(#1740): require-fs-op-fallback production AST rule + Windows transient-lock retry (Phase 6)

ADR-1703 Phase 6 of the cross-platform portability epic (#1702). Adds the
second production-code portability AST rule + the ADR-mandated glob expansion
to bin/install.js and scripts/build-hooks.js.

- eslint-rules/require-fs-op-fallback.cjs: flags an unguarded fs.rename /
  fs.renameSync (the atomic-publish primitive named first in
  DEFECT.WINDOWS-FS-OPS.symptom) that is NOT inside a try/catch whose handler
  references a transient errno ('EPERM'/'EBUSY'/'EACCES' or a *RETRY_ERRNOS
  set) AND NOT behind a Windows platform guard. A catch that silently swallows
  or cleans-up-and-rethrows without an errno check does NOT satisfy the
  defect's 'never silently swallow' clause. copyFile/unlink are deliberately
  not flagged (they are the fallback primitives per the defect's own
  fix-forward). Scope narrowed to rename per Phase 5's precision discipline;
  documented on #1740.

- src/shell-command-projection.cts: export retryRenameSync(from, to) — the
  drop-in bounded-retry helper over the existing atomicRenameWithRetry.

- 27 bare fs.renameSync sites across 11 modules routed through retryRenameSync
  (capability-lifecycle/lock/source, installer-migrations, milestone, phase,
  planning-workspace, roadmap-upgrade, runtime-hooks-surface, state,
  workstream). Idempotent on POSIX; resilient to AV/indexer transient locks
  on Windows.

- eslint.config.mjs: register rule at error on src/**/*.cts; new focused
  portability-rules block covering bin/install.js + scripts/build-hooks.js
  (ADR-1703 L124-126 glob expansion — both files are compliant: zero
  rename violations).

- tests: 15-case RuleTester suite; portability-rule-disable-ban extended
  (PROTECTED_RULES + scans bin/install.js/build-hooks.js with shebang
  handling); ci-test-scope portability-lint selection rule.

- CONTEXT.md DEFECT.WINDOWS-FS-OPS predicate rewritten to point at the rule;
  docs/contributing/cross-platform-portability-rules.md reference + how-to.

Closes #1740

* chore(#1740): backfill changeset pr:1742

* fix(#1740): tighten require-fs-op-fallback precision (codex review HIGH-1/HIGH-2)

Addresses two false-negative findings from the codex (gpt-5.5/high)
adversarial review of PR #1742:

HIGH-1 — a catch that REFERENCES a transient errno but only rethrows (no
retry/fallback) was marked compliant. The DEFECT.WINDOWS-FS-OPS fix-forward
requires retry, not just recognition. Fix: catchHandlerHasRetrySignal now
requires a loop `continue` backedge OR a `return <call>` delegation; a bare
rethrow is flagged. The misleading `/* retry logic */` valid test is replaced
with a real retry loop, and the rethrow-only shape is added as invalid.

HIGH-2 — the nested-try ancestor walk treated an OUTER errno-catch as
protecting the rename even when an INNER catch intercepted/swallowed the error
(the outer catch is unreachable). Fix: isInsideTransientErrnoTryCatch now stops
at the NEAREST enclosing TryStatement WITH A CATCH HANDLER whose block contains
the rename (try-finally is skipped — it doesn't catch); outer catches are no
longer consulted. The unsound nested-try valid test is converted to invalid,
and a try-finally-skipped valid case is added.

Verified: 17 RuleTester cases pass; zero new production violations (the 27
fixed sites use retryRenameSync; the real retry loops — atomicRenameWithRetry,
capability-ledger/consent, build-hooks — remain compliant via continue/errno);
lint:ci green; disable-ban + vocab-drift green.

---------

Co-authored-by: review-bot <review-bot@gsd>

src/capability-source.cts

@@ -34,6 +34,7 @@ const shellSeam = require('./shell-command-projection.cjs') as {
   execGit: (args: string[], opts?: { cwd?: string; timeout?: number }) => SpawnResult;
   execNpm: (args: string[], opts?: { cwd?: string; timeout?: number }) => SpawnResult;
   execTool: (program: string, args: string[], opts?: { cwd?: string; timeout?: number }) => SpawnResult;
+  retryRenameSync: (fromPath: string, toPath: string) => void;
 };
 
 // eslint-disable-next-line @typescript-eslint/no-require-imports
@@ -752,16 +753,16 @@ function stageValidated(opts: {
     // lives in capability-lifecycle.cjs and uses promote:false above.)
     if (fs.existsSync(finalDir)) {
       const backupDir = `${finalDir}.old-${process.pid}-${Date.now()}`;
-      fs.renameSync(finalDir, backupDir);
+      shellSeam.retryRenameSync(finalDir, backupDir);
       try {
-        fs.renameSync(stagingDir, finalDir);
+        shellSeam.retryRenameSync(stagingDir, finalDir);
       } catch (err) {
-        try { fs.renameSync(backupDir, finalDir); } catch { /* best-effort restore */ }
+        try { shellSeam.retryRenameSync(backupDir, finalDir); } catch { /* best-effort restore */ }
         throw err;
       }
       try { fs.rmSync(backupDir, { recursive: true, force: true }); } catch { /* best-effort */ }
     } else {
-      fs.renameSync(stagingDir, finalDir);
+      shellSeam.retryRenameSync(stagingDir, finalDir);
     }
 
     const version = typeof cap['version'] === 'string' ? cap['version'] : '';