docs(raw-api): document gitea_request, env vars and policy examples

Adds docs/raw-api.md (two-layer policy, sensitive denylist, env vars, write-mode
warning), links it from index and api-reference, documents RAW_API_ENABLED /
RAW_API_ALLOW_SENSITIVE in .env.example, and adds commented virtual-tool-name
deny examples to policy.yaml.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/api-reference.md

@@ -90,8 +90,18 @@ Scope requirements:
 - `create_milestone` (`owner`, `repo`, `title`, optional `description`, `due_on`)
 - `edit_issue_comment` (`owner`, `repo`, `comment_id`, `body`)
 
-Not supported by design: merge, branch/label/release deletion, force push, repo/admin
-management.
+Not supported by the dedicated tools by design: merge, branch/label/release deletion,
+force push, repo/admin management. Endpoints not covered above are reachable through the
+generic `gitea_request` escape hatch (subject to policy, write-mode, and a sensitive-path
+denylist) — see [Raw API Dispatch](raw-api.md).
+
+## Raw API Dispatch
+
+- `gitea_request` (`method`, `path`, optional `query`, `body`)
+  - Calls an arbitrary Gitea REST endpoint. `GET`/`HEAD` are reads; other methods are
+    writes and require write-mode plus a whitelisted repository. Admin/credential
+    endpoints are blocked unless `RAW_API_ALLOW_SENSITIVE=true`. See
+    [Raw API Dispatch](raw-api.md) for the two-layer policy model and full details.
 
 Note: `create_issue`, `add_labels`, and `remove_labels` accept label **names**; the
 server resolves them to Gitea label ids and returns a clear error for unknown labels.