fix(agent hooks): wire hooks into real harness entry points and fix payload parsing

Claude Code never reads a standalone .claude/hooks.json, so the PostToolUse and
Stop pipeline is moved into .claude/settings.json and hooks.json is removed;
.cursor/hooks.json is rewritten in Cursor's version+afterFileEdit/stop schema;
.codex/hooks.json is already Codex-valid and stays. The shared scripts now
parse both the Cursor file_path and Claude/Codex tool_input.file_path stdin
shapes and normalize absolute paths, so the format, yarn-install, and
react-pattern-review hooks stop being silent no-ops. verify.sh blocks with
exit 2 plus a stderr reason, guards stop_hook_active, and skips clean trees;
react-pattern-review surfaces its reminder via hookSpecificOutput on
PostToolUse; sync-git-branches no longer misreports open PRs as merged. The
validator now checks that the three harness-specific entry points wire the
same hook scripts instead of requiring byte-identical hooks.json copies.

scripts/agent-hooks/sync-git-branches.sh

@@ -45,6 +45,7 @@ branch_has_live_upstream() {
 merged_pr_number_for_branch() {
   local branch="$1"
   local pr_number=""
+  local merged_at=""
 
   if ! command -v gh >/dev/null 2>&1; then
     return 0
@@ -60,7 +61,10 @@ merged_pr_number_for_branch() {
   esac
 
   if [ -n "$pr_number" ]; then
-    gh pr view "$pr_number" --repo bitsocialnet/5chan --json mergedAt --jq 'select(.mergedAt != null) | .mergedAt' >/dev/null 2>&1 || return 0
+    # gh exits 0 even when the PR exists but is unmerged (the jq select just
+    # produces no output), so test the output instead of the exit code.
+    merged_at="$(gh pr view "$pr_number" --repo bitsocialnet/5chan --json mergedAt --jq 'select(.mergedAt != null) | .mergedAt' 2>/dev/null || true)"
+    [ -n "$merged_at" ] || return 0
     echo "$pr_number"
     return 0
   fi