feat: wire learnings into all insight-producing skills

Adds LEARNINGS_SEARCH and/or LEARNINGS_LOG to 10 skill templates that
produce reusable insights but were previously disconnected from the
learning system:

- office-hours, plan-ceo-review, plan-eng-review: add LOG (had SEARCH)
- plan-design-review: add both SEARCH + LOG (had neither)
- design-review, design-consultation, cso, qa, qa-only: add both
- retro: add SEARCH (had LOG)

13 skills now fully participate in the learning loop (read + write).
Every review, QA, investigation, and design session both consults prior
learnings and contributes new ones.

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

qa/SKILL.md.tmpl

@@ -90,6 +90,8 @@ mkdir -p .gstack/qa-reports/screenshots
 
 ---
 
+{{LEARNINGS_SEARCH}}
+
 ## Test Plan Context
 
 Before falling back to git diff heuristics, check for richer test plan sources:
@@ -315,6 +317,8 @@ If the repo has a `TODOS.md`:
 
 ---
 
+{{LEARNINGS_LOG}}
+
 ## Additional Rules (qa-specific)
 
 11. **Clean working tree required.** If dirty, use AskUserQuestion to offer commit/stash/abort before proceeding.