chore(#597): replace count-based ratchet guards with AST lint + named-set allowlists (#603)

The windows-test-parity ratchet greps test source for fs.rmSync-without-
maxRetries (and six other Windows-portability anti-patterns), failing when an
integer offender COUNT exceeds a frozen baseline (rmSync: 95). A count ratchet
is a Goodhart metric: fixing one offender and adding another keeps the count
constant, so a new defect slips through green. Replace it — and every other
count ratchet in the repo — with a layered, masking-proof design.

Behavioral seam test
- tests/helpers-cleanup.test.cjs proves helpers.cleanup() carries the Windows
  EBUSY retry budget. cleanup() delegates retries to Node's fs.rmSync via
  maxRetries (it owns no loop), so the test asserts the option contract
  (recursive/force/maxRetries>0/retryDelay>0) + real-FS removal + the cwd-guard,
  rather than a loop that does not exist. The EBUSY risk is now tested ONCE at
  the helper, not approximated textually at every call site.

Write-time ESLint rule (AST-accurate, replaces the grep)
- eslint-rules/no-raw-rmsync-in-tests.cjs (error in tests/**/*.test.cjs) bans
  raw fs.rmSync, steering to cleanup(). Catches member, computed (fs['rmSync']),
  destructured and aliased forms; escape hatch is inline
  `// eslint-disable-next-line local/no-raw-rmsync-in-tests -- <reason>` only.
- Migrated 336 raw fs.rmSync teardown calls across ~116 test files to cleanup().
  ~18 genuinely load-bearing sites (mid-test SUT/fault-injection removals,
  error-swallowing or name-colliding local teardown helpers) keep the raw call
  with an inline eslint-disable + reason.

Shared anti-ratchet primitive
- scripts/lib/allowlist-ratchet.cjs:
  - assertWithinAllowlist: fails on NOVEL ids (new offender introduced) AND on
    STALE ids (a known offender was fixed but not pruned) — identity, not count,
    and a ratchet DOWN toward zero.
  - assertTightCeiling: a size/length budget whose ceiling must stay within a
    grace band of the high-water mark, so budgets may only tighten, never creep.

Ratchets converted onto the primitive
- windows-test-parity-guard.test.cjs: rmSync rule deleted (now ESLint-enforced);
  the remaining six patterns moved from integer baselines to named-set
  allowlists with ratchet-down.
- scripts/lint-test-file-count.{cjs,allowlist.json}: per-module integer counts →
  named filename sets (closes the swap-a-file-keep-the-count blind spot); a
  module dropping under cap now FAILS to force pruning its allowlist entry.
- enh-2790 skill-count `<= 63` → named skill allowlist (ratchets toward ~58).

Size budgets hardened (tighten-only)
- agent-size / workflow-size / feat-3039 help-tiered: ceilings lowered to the
  current high-water mark and an assertTightCeiling anti-creep check added per
  tier. Fixed external-contract limits (description ≤100 chars, agent ≤100 KB)
  are intentionally left as-is — they are not grandfathered creeping budgets.

No user-facing behavior change (tests + tooling only); no USER_FACING_PREFIXES
touched, so no changeset fragment is required.

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

tests/core.test.cjs

@@ -1348,7 +1348,7 @@ describe('resolveWorktreeRoot with linked worktree .planning/', () => {
   afterEach(() => {
     if (worktreeDir) {
       try { execSyncLocal(`git worktree remove "${worktreeDir}" --force`, { cwd: mainDir, stdio: 'pipe' }); } catch { /* ok */ }
-      try { fs.rmSync(worktreeDir, { recursive: true, force: true }); } catch { /* ok */ }
+      cleanup(worktreeDir);
     }
     cleanup(mainDir);
   });
@@ -1359,7 +1359,7 @@ describe('resolveWorktreeRoot with linked worktree .planning/', () => {
 
     // Create a linked worktree
     worktreeDir = normalizePath(fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-wt-linked-')));
-    fs.rmSync(worktreeDir, { recursive: true, force: true });
+    cleanup(worktreeDir);
     execSyncLocal(`git worktree add "${worktreeDir}" -b test-linked`, { cwd: mainDir, stdio: 'pipe' });
 
     // Give the linked worktree its own .planning/
@@ -1374,7 +1374,7 @@ describe('resolveWorktreeRoot with linked worktree .planning/', () => {
   test('returns main repo root when linked worktree has no .planning/', () => {
     // Create a linked worktree (no .planning/ in main or worktree)
     worktreeDir = normalizePath(fs.mkdtempSync(path.join(os.tmpdir(), 'gsd-wt-linked-')));
-    fs.rmSync(worktreeDir, { recursive: true, force: true });
+    cleanup(worktreeDir);
     execSyncLocal(`git worktree add "${worktreeDir}" -b test-linked-no-plan`, { cwd: mainDir, stdio: 'pipe' });
 
     // resolveWorktreeRoot should return the main repo root
@@ -1473,7 +1473,7 @@ describe('detectSubRepos', () => {
   });
 
   afterEach(() => {
-    fs.rmSync(projectRoot, { recursive: true, force: true });
+    cleanup(projectRoot);
   });
 
   test('returns empty array when no child directories have .git', () => {
@@ -1520,7 +1520,7 @@ describe('loadConfig sub_repos auto-sync', () => {
   });
 
   afterEach(() => {
-    fs.rmSync(projectRoot, { recursive: true, force: true });
+    cleanup(projectRoot);
   });
 
   test('migrates multiRepo: true to sub_repos array', () => {
@@ -1590,7 +1590,7 @@ describe('findProjectRoot', () => {
   });
 
   afterEach(() => {
-    fs.rmSync(projectRoot, { recursive: true, force: true });
+    cleanup(projectRoot);
   });
 
   test('returns startDir when no .planning/ exists anywhere', () => {