feat: test coverage catalog + failure triage (merged branches) (#285)

* feat: add bin/gstack-repo-mode — solo vs collaborative detection with caching

Detects whether a repo is solo-dev (one person does 80%+ of recent commits)
or collaborative. Uses 90-day git shortlog window with 7-day cache in
~/.gstack/projects/{SLUG}/repo-mode.json. Config override via
`gstack-config set repo_mode solo|collaborative` takes precedence over
the heuristic. Minimum 5 commits required to classify (otherwise unknown).

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

* feat: test failure ownership triage — see something say something

Adds two new preamble sections to all gstack skills:
- Repo Ownership Mode: explains solo vs collaborative behavior
- See Something, Say Something: proactive issue flagging principle

Adds {{TEST_FAILURE_TRIAGE}} template variable (opt-in, used by /ship):
- Classifies test failures as in-branch vs pre-existing
- Solo mode defaults to "investigate and fix now"
- Collaborative mode offers "blame + assign GitHub issue" option
- Also offers P0 TODO and skip options

/ship Step 3 now triages test failures instead of hard-stopping on all
failures. In-branch failures still block shipping. Pre-existing failures
get user-directed triage based on repo mode.

Adds P2 TODO for gstack notes system (deferred lightweight reminder).

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

* chore: regenerate SKILL.md files for Claude and Codex hosts

All 22 Claude skills and 21 Codex skills regenerated with new preamble
sections (Repo Ownership Mode, See Something Say Something) and
{{TEST_FAILURE_TRIAGE}} resolved in ship/SKILL.md.

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

* fix: validate repo mode values to prevent shell injection

Codex adversarial review found that unvalidated config/cache values
could be injected into shell via source <(gstack-repo-mode). Added
validate_mode() that only allows solo|collaborative|unknown — anything
else becomes "unknown". Prevents persistent code execution through
malicious config.yaml or tampered cache JSON.

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

* fix: shell injection via branch names + feature-branch sampling bias

Codex code review found two issues:

P1: eval $(gstack-slug) in gstack-repo-mode executes branch names as
shell. Branch names like foo$(touch${IFS}pwned) are valid git refs and
would execute arbitrary commands. Fix: compute SLUG directly with sed
instead of eval'ing gstack-slug output.

P2: git shortlog HEAD only sees current branch history. On feature
branches that haven't merged main recently, other contributors disappear
from the sample. Fix: use git shortlog on the default branch
(origin/main) instead of HEAD.

Also improved blame lookup in collaborative triage to check both the
test file and the production code it covers.

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

* fix: broaden codex-host stripping test to accommodate triage section

"Investigate and fix" now appears in TEST_FAILURE_TRIAGE (not just the
Codex review step). Use CODEX_REVIEWS config string as a more specific
marker for detecting the Codex review step in Codex-hosted skills.

* fix: replace template placeholder in TODOS.md with readable text

{{TEST_FAILURE_TRIAGE}} is template syntax but TODOS.md is not processed
by gen-skill-docs — replaced with human-readable reference.

* chore: bump version and changelog (v0.9.5.0)

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

* docs: add bin/ directory to project structure in CLAUDE.md

* test: add triage resolver unit tests, plan-eng coverage audit E2E, and triage E2E

- TEST_FAILURE_TRIAGE resolver: 6 unit tests verifying all triage steps (T1-T4),
  REPO_MODE branching, and safety default for ambiguous failures
- plan-eng-coverage-audit E2E: tests /plan-eng-review coverage audit codepath
  (gap identified during eng review — existed on neither branch)
- ship-triage E2E: planted-bug fixture with in-branch (truncate null) and
  pre-existing (divide-by-zero) failures; verifies correct classification
- Touchfile entries for diff-based test selection

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

* chore: regenerate stale Codex SKILL.md for retro

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

---------

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

test/skill-validation.test.ts

@@ -1280,12 +1280,12 @@ describe('Codex skill', () => {
   test('codex-host ship/review do NOT contain codex review step', () => {
     const shipContent = fs.readFileSync(path.join(ROOT, '.agents', 'skills', 'gstack-ship', 'SKILL.md'), 'utf-8');
     expect(shipContent).not.toContain('codex review --base');
-    expect(shipContent).not.toContain('Investigate and fix');
+    expect(shipContent).not.toContain('CODEX_REVIEWS');
 
     const reviewContent = fs.readFileSync(path.join(ROOT, '.agents', 'skills', 'gstack-review', 'SKILL.md'), 'utf-8');
     expect(reviewContent).not.toContain('codex review --base');
     expect(reviewContent).not.toContain('codex_reviews');
-    expect(reviewContent).not.toContain('Investigate and fix');
+    expect(reviewContent).not.toContain('CODEX_REVIEWS');
   });
 
   test('codex integration in /plan-eng-review offers plan critique', () => {
@@ -1411,3 +1411,58 @@ describe('Codex skill validation', () => {
     }
   });
 });
+
+// --- Repo mode and test failure triage validation ---
+
+describe('Repo mode preamble validation', () => {
+  test('generated SKILL.md preamble contains REPO_MODE output', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'SKILL.md'), 'utf-8');
+    expect(content).toContain('REPO_MODE:');
+    expect(content).toContain('gstack-repo-mode');
+  });
+
+  test('generated SKILL.md contains See Something Say Something section', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'SKILL.md'), 'utf-8');
+    expect(content).toContain('See Something, Say Something');
+    expect(content).toContain('REPO_MODE');
+    expect(content).toContain('solo');
+    expect(content).toContain('collaborative');
+  });
+});
+
+describe('Test failure triage in ship skill', () => {
+  test('ship/SKILL.md contains Test Failure Ownership Triage', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'ship', 'SKILL.md'), 'utf-8');
+    expect(content).toContain('Test Failure Ownership Triage');
+  });
+
+  test('ship/SKILL.md triage uses git diff for classification', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'ship', 'SKILL.md'), 'utf-8');
+    expect(content).toContain('git diff origin/<base>...HEAD --name-only');
+  });
+
+  test('ship/SKILL.md triage has solo and collaborative paths', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'ship', 'SKILL.md'), 'utf-8');
+    expect(content).toContain('REPO_MODE');
+    expect(content).toContain('solo');
+    expect(content).toContain('collaborative');
+    expect(content).toContain('Investigate and fix now');
+    expect(content).toContain('Add as P0 TODO');
+  });
+
+  test('ship/SKILL.md triage has GitHub issue assignment for collaborative mode', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'ship', 'SKILL.md'), 'utf-8');
+    expect(content).toContain('gh issue create');
+    expect(content).toContain('--assignee');
+  });
+
+  test('{{TEST_FAILURE_TRIAGE}} placeholder is fully resolved in ship/SKILL.md', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'ship', 'SKILL.md'), 'utf-8');
+    expect(content).not.toContain('{{TEST_FAILURE_TRIAGE}}');
+  });
+
+  test('ship/SKILL.md uses in-branch language for stop condition', () => {
+    const content = fs.readFileSync(path.join(ROOT, 'ship', 'SKILL.md'), 'utf-8');
+    expect(content).toContain('In-branch test failures');
+  });
+});