Merge origin/main (v1.64.1.0 code-smell wave) into test-evals-ci-speedup

Both sides shipped overlapping test-infra work in parallel; resolutions
compose intent rather than picking sides:

- free-tests.yml (both added): keep this branch's lane (canonical
  strict-parallel runner, secretless, plain runner, ~2min) over main's
  per-file-serial container loop (45min budget, hand-curated skip list,
  needs GITHUB_TOKEN); ported main's git safe.directory insight.
- Dockerfile.ci Bun install: main discovered the installer IGNORES the
  BUN_VERSION env var (the old form silently installed latest) — main's
  arg-form mechanism + this branch's 1.3.13 target.
- parity baseline: both sides rebased after hitting the same silent
  drift; adopted main's v1.64.1.0 union-normalized fixture and dropped
  this branch's interim v1.64.0.0 capture. carve-guards caps: main's
  tighter re-ratchets win (all four).
- touchfiles: kept this branch's three-file facade split; ported main's
  pure-data removals (dead sidebar-agent entries, spec judge entry,
  ship-idempotency) into touchfiles-data.ts.
- ship-idempotency SDK variant: main deliberately removed it as
  redundant with the real-PTY test; adopted — dropped this branch's
  rehomed copy and its periodic matrix row (the zombie-monolith deletion
  stands; coverage-audit + triage rehomes verified untouched by main).
- e2e-tier-alignment: taught the new parent-mapper hard check main's
  consolidated describeE2ETier()/e2eTierEnabled() self-gate shapes (the
  helper's header names this file as a required recognizer).
- browse/test/compare-board.test.ts: quarantined behind
  GSTACK_COMPARE_BOARD_TESTS=1 — all 16 tests fail identically on
  origin/main solo on dev machines (blame protocol receipts in-file);
  main's own CI lane skip-lists it. An always-red file would block every
  PR now that free-tests is a required check.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/skill-size-budget.test.ts

@@ -167,12 +167,28 @@ describe('SKILL.md size budget regression (gate, free)', () => {
     // skeleton+sections union), so exempt the skeleton from the body-strip floor.
     // EQ1: derived from the canonical CARVE_GUARDS registry — no parallel list.
     const SECTIONS_EXTRACTED = new Set<string>(CARVED_SKILLS);
+    // Intentional one-off shrinks vs the frozen baseline (each needs a reason):
+    // - spec: the baseline measured a template bug — prose at Phase 5 mentioned
+    //   {{PREAMBLE}} literally, so the generator expanded the ENTIRE preamble a
+    //   second time mid-sentence (~47 KB of duplication). Fixed by rewording the
+    //   prose; spec/SKILL.md now carries exactly one preamble (~80.9 KB, ×0.79).
+    // - scrape/diagram/open-gstack-browser/landing-report/pair-agent/skillify:
+    //   the baseline measured these at the silent tier-4 default (a missing
+    //   preamble-tier frontmatter fell through `?? 4`). Their tiers are now
+    //   declared correctly (1-2), shedding the tier-2..4 onboarding prose they
+    //   never should have carried (-271 lines each for tier 1).
+    const INTENTIONAL_SHRINKS = new Set<string>([
+      'spec',
+      'scrape', 'diagram', 'open-gstack-browser',
+      'landing-report', 'pair-agent', 'skillify',
+    ]);
 
     const undershoots: Array<{
       skill: string; beforeBytes: number; afterBytes: number; ratio: number;
     }> = [];
     for (const [skill, before] of Object.entries(baseline.skills)) {
       if (SECTIONS_EXTRACTED.has(skill)) continue;
+      if (INTENTIONAL_SHRINKS.has(skill)) continue;
       const after = current.skills[skill];
       if (!after) continue; // skill removed since baseline — separate concern
       const ratio = after.skillMdBytes / before.skillMdBytes;