docs(AGENTS): document GITEA_ACCESS_TOKEN env for general Gitea API access

GITEA_ACCESS_TOKEN + GITEA_HOST (passed from host .env via compose,
primarily for gitea-mcp) are also usable for any direct Gitea API work —
run inspection, tag checks — not just ci-release-watcher. Prefer over a
PAT file when present; host-managed lifecycle, nothing to revoke. Release
checklist step 7 now notes the env-token alternative.

AGENTS.md

@@ -61,7 +61,24 @@ re-brand of opencode-devbox's `pi-only` variant.
 6. Verify the Hub tags appear (latest + vX.Y.Z, the `-studio` pair, plus
    base-latest if the base was rebuilt this run).
 7. **Revoke any short-lived Gitea PAT** used during the release at
-   `gitea.jordbo.se/user/settings/applications`.
+   `gitea.jordbo.se/user/settings/applications`. N/A if you used the
+   `GITEA_ACCESS_TOKEN` env var instead (see *Gitea API access* below) —
+   its lifecycle is managed host-side, nothing to revoke.
+
+## Gitea API access (env token)
+
+`GITEA_ACCESS_TOKEN` + `GITEA_HOST` are passed into the container from the
+host `.env` via `docker-compose.yml` (`${GITEA_ACCESS_TOKEN:-}` /
+`${GITEA_HOST:-}`), primarily to enable the `gitea-mcp` server. They are
+**not** baked into the image. When configured, they are also available for
+**any** direct Gitea API interaction from inside the container — inspecting
+CI runs, checking published tags, listing commits — e.g.
+`curl -H "Authorization: token $GITEA_ACCESS_TOKEN" "$GITEA_HOST/api/v1/repos/joakimp/pi-devbox/actions/runs?limit=5"`.
+Prefer this over a short-lived PAT file when the env token is present (the
+`ci-release-watcher` skill auto-detects it). Public-repo GET listings work
+unauthenticated too, so the token matters mainly for private repos or
+rate-limit headroom; its lifecycle is host-managed, so there is nothing to
+revoke after use. Never echo the token value (including into logs).
 
 ## Cache-hit footgun (must-know)