feat: contributor mode, session awareness, recommendation format (#90)

* feat: contributor mode, session awareness, universal RECOMMENDATION format

- Rename {{UPDATE_CHECK}} → {{PREAMBLE}} across all 10 skill templates
- Add session tracking (touch ~/.gstack/sessions/$PPID, count active sessions)
- ELI16 mode when 3+ concurrent sessions detected (re-ground user on context)
- Contributor mode: auto-file field reports to ~/.gstack/contributor-logs/
- Universal AskUserQuestion format: context → question → RECOMMENDATION → options
- Update plan-ceo-review and plan-eng-review to reference preamble baseline
- Add vendored symlink awareness section to CLAUDE.md
- Rewrite CONTRIBUTING.md with contributor workflow and cross-project testing
- Add tests for contributor mode and session awareness in generated output
- Add E2E eval for contributor mode report filing

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: add Enum & Value Completeness to /review critical checklist

New CRITICAL review category that traces new enum values, status strings,
and type constants through every consumer outside the diff. Catches the
class of bugs where a new value is added but not handled in all switch/case
chains, allowlists, or frontend-backend contracts.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* chore: bump v0.4.1, user-facing changelog, update qa-only template and architecture docs

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: add CHANGELOG style guide — user-facing, sell the feature

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* docs: rewrite v0.4.1 changelog to be user-facing and sell the features

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add evals for RECOMMENDATION format, session awareness, and enum completeness

Free tests (Tier 1): RECOMMENDATION format + session awareness in all
preamble SKILL.md files, enum completeness checklist structure and CRITICAL
classification.

E2E eval: /review catches missed enum handlers when a new status value
is added but not handled in case/switch and notify methods.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add E2E eval for session awareness ELI16 mode

Stubs _SESSIONS=4, gives agent a decision point on feature/add-payments
branch, verifies the output re-grounds the user with project, branch,
context, and RECOMMENDATION — the ELI16 mode behavior for 3+ sessions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: contributor mode eval marked FAIL due to expected browse error

The test intentionally runs a nonexistent binary to trigger contributor
mode. The session runner's browse error detection catches "no such file
or directory...browse" and sets browseErrors, causing recordE2E to mark
passed=false. Override passed to check only exitReason since the browse
error is the expected scenario.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

test/skill-validation.test.ts

@@ -411,6 +411,66 @@ describe('TODOS-format.md reference consistency', () => {
   });
 });
 
+// --- v0.4.1 feature coverage: RECOMMENDATION format, session awareness, enum completeness ---
+
+describe('v0.4.1 preamble features', () => {
+  const skillsWithPreamble = [
+    'SKILL.md', 'browse/SKILL.md', 'qa/SKILL.md',
+    'qa-only/SKILL.md',
+    'setup-browser-cookies/SKILL.md',
+    'ship/SKILL.md', 'review/SKILL.md',
+    'plan-ceo-review/SKILL.md', 'plan-eng-review/SKILL.md',
+    'retro/SKILL.md',
+  ];
+
+  for (const skill of skillsWithPreamble) {
+    test(`${skill} contains RECOMMENDATION format`, () => {
+      const content = fs.readFileSync(path.join(ROOT, skill), 'utf-8');
+      expect(content).toContain('RECOMMENDATION: Choose');
+      expect(content).toContain('AskUserQuestion');
+    });
+
+    test(`${skill} contains session awareness`, () => {
+      const content = fs.readFileSync(path.join(ROOT, skill), 'utf-8');
+      expect(content).toContain('_SESSIONS');
+      expect(content).toContain('ELI16');
+    });
+  }
+});
+
+describe('Enum & Value Completeness in review checklist', () => {
+  const checklist = fs.readFileSync(path.join(ROOT, 'review', 'checklist.md'), 'utf-8');
+
+  test('checklist has Enum & Value Completeness section', () => {
+    expect(checklist).toContain('Enum & Value Completeness');
+  });
+
+  test('Enum & Value Completeness is classified as CRITICAL', () => {
+    // It should appear under Pass 1 — CRITICAL, not Pass 2
+    const pass1Start = checklist.indexOf('### Pass 1');
+    const pass2Start = checklist.indexOf('### Pass 2');
+    const enumStart = checklist.indexOf('Enum & Value Completeness');
+    expect(enumStart).toBeGreaterThan(pass1Start);
+    expect(enumStart).toBeLessThan(pass2Start);
+  });
+
+  test('Enum & Value Completeness mentions tracing through consumers', () => {
+    expect(checklist).toContain('Trace it through every consumer');
+    expect(checklist).toContain('case');
+    expect(checklist).toContain('allowlist');
+  });
+
+  test('Enum & Value Completeness is in the gate classification as CRITICAL', () => {
+    const gateSection = checklist.slice(checklist.indexOf('## Gate Classification'));
+    // The ASCII art has CRITICAL on the left and INFORMATIONAL on the right
+    // Enum & Value Completeness should appear on a line with the CRITICAL tree (├─ or └─)
+    const enumLine = gateSection.split('\n').find(l => l.includes('Enum & Value Completeness'));
+    expect(enumLine).toBeDefined();
+    // It's on the left (CRITICAL) side — starts with ├─ or └─
+    expect(enumLine!.trimStart().startsWith('├─') || enumLine!.trimStart().startsWith('└─')).toBe(true);
+  });
+});
+
 // --- Part 7: Planted-bug fixture validation (A4) ---
 
 describe('Planted-bug fixture validation', () => {