feat: integrate learnings + confidence into 9 skill templates

Add {{LEARNINGS_SEARCH}}, {{LEARNINGS_LOG}}, and {{CONFIDENCE_CALIBRATION}}
placeholders to review, ship, plan-eng-review, plan-ceo-review, office-hours,
investigate, retro, and cso templates. Regenerated all SKILL.md files.

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

office-hours/SKILL.md

@@ -66,6 +66,15 @@ for _PF in $(find ~/.gstack/analytics -maxdepth 1 -name '.pending-*' 2>/dev/null
   fi
   break
 done
+# Learnings count
+eval "$(~/.claude/skills/gstack/bin/gstack-slug 2>/dev/null)" 2>/dev/null || true
+_LEARN_FILE="${GSTACK_HOME:-$HOME/.gstack}/projects/${SLUG:-unknown}/learnings.jsonl"
+if [ -f "$_LEARN_FILE" ]; then
+  _LEARN_COUNT=$(wc -l < "$_LEARN_FILE" 2>/dev/null | tr -d ' ')
+  echo "LEARNINGS: $_LEARN_COUNT entries loaded"
+else
+  echo "LEARNINGS: 0"
+fi
 ```
 
 If `PROACTIVE` is `"false"`, do not proactively suggest gstack skills AND do not
@@ -400,6 +409,44 @@ eval "$(~/.claude/skills/gstack/bin/gstack-slug 2>/dev/null)"
    ```
    If design docs exist, list them: "Prior designs for this project: [titles + dates]"
 
+## 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.
+
 5. **Ask: what's your goal with this?** This is a real question, not a formality. The answer determines everything about how the session runs.
 
    Via AskUserQuestion, ask:

office-hours/SKILL.md.tmpl

@@ -53,6 +53,8 @@ Understand the project and the area the user wants to change.
    ```
    If design docs exist, list them: "Prior designs for this project: [titles + dates]"
 
+{{LEARNINGS_SEARCH}}
+
 5. **Ask: what's your goal with this?** This is a real question, not a formality. The answer determines everything about how the session runs.
 
    Via AskUserQuestion, ask: