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>

.env.example

@@ -63,6 +63,17 @@ WRITE_MODE=false
 WRITE_REPOSITORY_WHITELIST=
 WRITE_ALLOW_ALL_TOKEN_REPOS=false
 
+# Raw API dispatch (gitea_request escape hatch). See docs/raw-api.md.
+# gitea_request can call any Gitea REST endpoint (method + path). It is still
+# subject to policy.yaml, WRITE_MODE + the write whitelist, and a built-in
+# admin/credential denylist. Set RAW_API_ENABLED=false to remove the tool's
+# ability to dispatch entirely.
+RAW_API_ENABLED=true
+# Allow gitea_request to reach admin/credential surfaces (/admin, *tokens*,
+# *secrets*, *hooks*, *keys*, applications/oauth2, runner registration tokens).
+# Leave false unless you fully understand the exposure.
+RAW_API_ALLOW_SENSITIVE=false
+
 # Automation mode (disabled by default)
 AUTOMATION_ENABLED=false
 AUTOMATION_SCHEDULER_ENABLED=false