chore: ignore local PID files and Graphify AST/incremental caches

Stop tracking runtime PID and regenerable Graphify cache/state so they no longer clutter git status.

Co-authored-by: Cursor <cursoragent@cursor.com>

.gitignore

@@ -84,3 +84,13 @@ exports/
 
 # Local git worktrees (isolated feature checkouts)
 .worktrees/
+
+# 本地进程 PID（如 backend/app.pid，由 start-*.sh 写入，勿提交）
+*.pid
+
+# Graphify：AST 解析缓存（体积大、可本地再生成；常见于 backend/app/、web-admin/src/ 下）
+**/graphify-out/cache/
+
+# Graphify：增量检测/状态文件（commit hook 或 update-graph.sh 触发后产生）
+**/.graphify_detect.json
+**/.graphify_incremental.json