docs(agents): treat ccc index / ccc init as read-safe maintenance

agents/AGENTS.md

@@ -36,3 +36,8 @@
   it, results are filtered to the current working directory's
   subtree. The `ccc` skill has the full reference;
   `grep`/`rg`/`find` remain fine for exact-string lookups.
+- **`ccc index` / `ccc init` are read-safe maintenance.** They only
+  write to the gitignored `.cocoindex_code/` directory, never to
+  source. Run them without confirmation prompts — at session start,
+  after refactors, or before a search when the index may be stale.
+  Treat like `grep` for permission purposes, not like a code edit.