Add git/docs rules to AGENTS.md; add docs reminder to presubmit

AGENTS.md

@@ -8,6 +8,12 @@
 ## Implementation rules
 - No backward-compatibility shims or legacy endpoint aliases.
 - Run `poetry run presubmit` before finishing any task. Fix all failures before marking work done.
+- Before marking a task done: update `docs/overview.md` if the change affects architecture, layer boundaries, config schema, directory layout, API endpoints, or the plugin system. Do not update it for implementation details.
+
+## Git rules
+- Never set or modify git config (`git config` or `git -c user.*`) without an explicit request from the user.
+- Respect whatever author/email is already configured in the repository or global git config.
+- If a commit requires author information that is missing, ask the user rather than inventing values.
 
 ## Documentation rules
 Follow `docs/contributing.md`. Key points:

scripts/presubmit.py

@@ -53,3 +53,7 @@ def presubmit():
         print(f"\nFailed: {', '.join(failed)}", file=sys.stderr)
         sys.exit(1)
     print("\nAll presubmit checks passed.")
+    print(
+        "\nReminder: if this task changed architecture, layer boundaries, config schema,\n"
+        "directory layout, API endpoints, or the plugin system — update docs/overview.md."
+    )