docs: add extension management guidance

llm.txt

@@ -6,6 +6,7 @@ Important files:
 
 - `AGENTS.md`: Project instructions for coding agents.
 - `manifest.llm.json`: Machine-readable project metadata.
+- `docs/extension-management.md`: Chrome extension management instructions, including the required Chrome profile.
 - `.env.example`: Required environment variables.
 - `vite.config.ts`: Vite build config and generated Chrome extension manifest logic.
 - `src/api.ts`: Axios client and Gitea configuration handling.
@@ -15,6 +16,8 @@ Important files:
 
 Build with `npm run build`. The deployable output directory is `dist/`; load that folder in Chrome as an unpacked extension or point deployment tooling at it. Do not edit `dist/` directly.
 
+Extension management rule: use the Codex Chrome extension with the Chrome profile named `Silma`. Do not use `Profile 1`.
+
 Codex commands:
 
 - Setup: `npm run codex:setup`
@@ -28,3 +31,8 @@ Required env variables:
 - `VITE_GITEA_TOKEN`
 - `VITE_GITEA_REPO_OWNER`
 - `VITE_GITEA_REPO_NAME`
+
+Gitea workflows:
+
+- `.gitea/workflows/build.yml`: build validation for pushes to `main` and pull requests.
+- `.gitea/workflows/issue-opened-placeholder.yml`: new issue placeholder that prints `200 okay`.