Add Gitea integration for agent to push branches and open pull requests

- Implemented `register-gitea-bot.sh` to provision Gitea access token.
- Updated `maintainer.py` to support Gitea API for push and PR operations.
- Modified `install.sh` to warn if Gitea token is not provisioned.
- Enhanced documentation in `README.md`, `CLAUDE.md`, and `architecture.md` to reflect new Gitea functionality.
- Added Gitea configuration to `config.example.json`.

install.sh

@@ -27,6 +27,13 @@ case "$TOKEN" in
   ""|FILLED_BY_*) echo "ERROR: Matrix not provisioned. Run register-matrix-bot.sh first."; exit 1;;
 esac
 
+# Gitea (push/PR capability) is optional — warn but don't block if unprovisioned.
+GTOK="$(python3 -c "import json;print(json.load(open('$DIR/config.json')).get('gitea',{}).get('token',''))")"
+case "$GTOK" in
+  ""|FILLED_BY_*) echo "WARN: Gitea not provisioned — the agent will not push or open PRs.";
+                  echo "      Run register-gitea-bot.sh to enable it.";;
+esac
+
 echo "→ Syntax-checking maintainer.py"
 python3 -m py_compile "$DIR/maintainer.py"