fix(hooks): nest freeze/careful permissionDecision under hookSpecificOutput

Claude Code ignores a top-level permissionDecision, so the /freeze deny and
/careful ask guards silently allowed everything. Nest both under
hookSpecificOutput with permissionDecisionReason, update the shape-blind
tests to pin the nested form, and document the constraint in both skill
templates (regen included).

Closes half of #1459 (freeze enforcement chain).

Contributed by @jawadakram20 (PR #2331; team-init hunk deferred to the
dedicated team-init fix).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

careful/bin/check-careful.sh

@@ -1,7 +1,9 @@
 #!/usr/bin/env bash
 # check-careful.sh — PreToolUse hook for /careful skill
 # Reads JSON from stdin, checks Bash command for destructive patterns.
-# Returns {"permissionDecision":"ask","message":"..."} to warn, or {} to allow.
+# Returns a PreToolUse hookSpecificOutput with permissionDecision "ask" to warn,
+# or {} to allow. The decision MUST be nested under hookSpecificOutput — Claude
+# Code ignores a top-level permissionDecision, which silently no-ops the warning.
 set -euo pipefail
 
 # Read stdin (JSON with tool_input)
@@ -101,7 +103,7 @@ if [ -n "$WARN" ]; then
   echo '{"event":"hook_fire","skill":"careful","pattern":"'"$PATTERN"'","ts":"'$(date -u +%Y-%m-%dT%H:%M:%SZ)'","repo":"'$(basename "$(git rev-parse --show-toplevel 2>/dev/null)" 2>/dev/null || echo "unknown")'"}' >> ~/.gstack/analytics/skill-usage.jsonl 2>/dev/null || true
 
   WARN_ESCAPED=$(printf '%s' "$WARN" | sed 's/"/\\"/g')
-  printf '{"permissionDecision":"ask","message":"[careful] %s"}\n' "$WARN_ESCAPED"
+  printf '{"hookSpecificOutput":{"hookEventName":"PreToolUse","permissionDecision":"ask","permissionDecisionReason":"[careful] %s"}}\n' "$WARN_ESCAPED"
 else
   echo '{}'
 fi