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>

plan-design-review/SKILL.md

@@ -860,6 +860,44 @@ descriptions of what 10/10 looks like.
 
 ## Review Sections (7 passes, after scope is agreed)
 
+## Prior Learnings
+
+Search for relevant learnings from previous sessions:
+
+```bash
+_CROSS_PROJ=$(~/.claude/skills/gstack/bin/gstack-config get cross_project_learnings 2>/dev/null || echo "unset")
+echo "CROSS_PROJECT: $_CROSS_PROJ"
+if [ "$_CROSS_PROJ" = "true" ]; then
+  ~/.claude/skills/gstack/bin/gstack-learnings-search --limit 10 --cross-project 2>/dev/null || true
+else
+  ~/.claude/skills/gstack/bin/gstack-learnings-search --limit 10 2>/dev/null || true
+fi
+```
+
+If `CROSS_PROJECT` is `unset` (first time): Use AskUserQuestion:
+
+> gstack can search learnings from your other projects on this machine to find
+> patterns that might apply here. This stays local (no data leaves your machine).
+> Recommended for solo developers. Skip if you work on multiple client codebases
+> where cross-contamination would be a concern.
+
+Options:
+- A) Enable cross-project learnings (recommended)
+- B) Keep learnings project-scoped only
+
+If A: run `~/.claude/skills/gstack/bin/gstack-config set cross_project_learnings true`
+If B: run `~/.claude/skills/gstack/bin/gstack-config set cross_project_learnings false`
+
+Then re-run the search with the appropriate flag.
+
+If learnings are found, incorporate them into your analysis. When a review finding
+matches a past learning, display:
+
+**"Prior learning applied: [key] (confidence N/10, from [date])"**
+
+This makes the compounding visible. The user should see that gstack is getting
+smarter on their codebase over time.
+
 ### Pass 1: Information Architecture
 Rate 0-10: Does the plan define what the user sees first, second, third?
 FIX TO 10: Add information hierarchy to the plan. Include ASCII diagram of screen/page structure and navigation flow. Apply "constraint worship" — if you can only show 3 things, which 3?
@@ -1215,6 +1253,31 @@ plan's living status.
 - Always place it as the very last section in the plan file. If it was found mid-file,
   move it: delete the old location and append at the end.
 
+## Capture Learnings
+
+If you discovered a non-obvious pattern, pitfall, or architectural insight during
+this session, log it for future sessions:
+
+```bash
+~/.claude/skills/gstack/bin/gstack-learnings-log '{"skill":"plan-design-review","type":"TYPE","key":"SHORT_KEY","insight":"DESCRIPTION","confidence":N,"source":"SOURCE","files":["path/to/relevant/file"]}'
+```
+
+**Types:** `pattern` (reusable approach), `pitfall` (what NOT to do), `preference`
+(user stated), `architecture` (structural decision), `tool` (library/framework insight),
+`operational` (project environment/CLI/workflow knowledge).
+
+**Sources:** `observed` (you found this in the code), `user-stated` (user told you),
+`inferred` (AI deduction), `cross-model` (both Claude and Codex agree).
+
+**Confidence:** 1-10. Be honest. An observed pattern you verified in the code is 8-9.
+An inference you're not sure about is 4-5. A user preference they explicitly stated is 10.
+
+**files:** Include the specific file paths this learning references. This enables
+staleness detection: if those files are later deleted, the learning can be flagged.
+
+**Only log genuine discoveries.** Don't log obvious things. Don't log things the user
+already knows. A good test: would this insight save time in a future session? If yes, log it.
+
 ## Next Steps — Review Chaining
 
 After displaying the Review Readiness Dashboard, recommend the next review(s) based on what this design review discovered. Read the dashboard output to see which reviews have already been run and whether they are stale.

plan-design-review/SKILL.md.tmpl

@@ -257,6 +257,8 @@ descriptions of what 10/10 looks like.
 
 ## Review Sections (7 passes, after scope is agreed)
 
+{{LEARNINGS_SEARCH}}
+
 ### Pass 1: Information Architecture
 Rate 0-10: Does the plan define what the user sees first, second, third?
 FIX TO 10: Add information hierarchy to the plan. Include ASCII diagram of screen/page structure and navigation flow. Apply "constraint worship" — if you can only show 3 things, which 3?
@@ -431,6 +433,8 @@ Substitute values from the Completion Summary:
 
 {{PLAN_FILE_REVIEW_REPORT}}
 
+{{LEARNINGS_LOG}}
+
 ## Next Steps — Review Chaining
 
 After displaying the Review Readiness Dashboard, recommend the next review(s) based on what this design review discovered. Read the dashboard output to see which reviews have already been run and whether they are stale.