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>

test/helpers/touchfiles.ts

@@ -64,7 +64,7 @@ export const E2E_TOUCHFILES: Record<string, string[]> = {
   'plan-eng-review-artifact':  ['plan-eng-review/**'],
 
   // Ship
-  'ship-base-branch': ['ship/**'],
+  'ship-base-branch': ['ship/**', 'bin/gstack-repo-mode'],
 
   // Retro
   'retro':             ['retro/**'],
@@ -84,7 +84,7 @@ export const E2E_TOUCHFILES: Record<string, string[]> = {
   'qa-bootstrap': ['qa/**', 'browse/src/**', 'ship/**'],
 
   // Ship coverage audit
-  'ship-coverage-audit': ['ship/**'],
+  'ship-coverage-audit': ['ship/**', 'bin/gstack-repo-mode'],
 
   // Design
   'design-consultation-core':     ['design-consultation/**'],