feat: add proactive triggers to all workflow skills

Every skill now has "Proactively suggest when..." language so Claude
surfaces skills at natural moments — not just when the user says
specific trigger phrases.

review/SKILL.md

@@ -5,6 +5,7 @@ description: |
   Pre-landing PR review. Analyzes diff against the base branch for SQL safety, LLM trust
   boundary violations, conditional side effects, and other structural issues. Use when
   asked to "review this PR", "code review", "pre-landing review", or "check my diff".
+  Proactively suggest when the user is about to merge or land code changes.
 allowed-tools:
   - Bash
   - Read
@@ -31,8 +32,13 @@ _BRANCH=$(git branch --show-current 2>/dev/null || echo "unknown")
 echo "BRANCH: $_BRANCH"
 _LAKE_SEEN=$([ -f ~/.gstack/.completeness-intro-seen ] && echo "yes" || echo "no")
 echo "LAKE_INTRO: $_LAKE_SEEN"
+_PROACTIVE=$(~/.claude/skills/gstack/bin/gstack-config get proactive 2>/dev/null || echo "true")
+echo "PROACTIVE: $_PROACTIVE"
 ```
 
+If `PROACTIVE` is `"false"`, do not proactively suggest gstack skills — only invoke
+them when the user explicitly asks. The user opted out of proactive suggestions.
+
 If output shows `UPGRADE_AVAILABLE <old> <new>`: read `~/.claude/skills/gstack/gstack-upgrade/SKILL.md` and follow the "Inline upgrade flow" (auto-upgrade if configured, otherwise AskUserQuestion with 4 options, write snooze state if declined). If `JUST_UPGRADED <from> <to>`: tell user "Running gstack v{to} (just updated!)" and continue.
 
 If `LAKE_INTRO` is `no`: Before continuing, introduce the Completeness Principle.

review/SKILL.md.tmpl

@@ -5,6 +5,7 @@ description: |
   Pre-landing PR review. Analyzes diff against the base branch for SQL safety, LLM trust
   boundary violations, conditional side effects, and other structural issues. Use when
   asked to "review this PR", "code review", "pre-landing review", or "check my diff".
+  Proactively suggest when the user is about to merge or land code changes.
 allowed-tools:
   - Bash
   - Read