ci: use Docs Agent API key so per-agent secrets are available

Replace WARP_API_KEY with DOCS_AGENT_WARP_API_KEY in the release
docs update workflow. Running under the Docs Agent's own API key
makes its per-agent secrets (DOCS_AGENT_GRAFANA_TOKEN) available
in the cloud run environment for on-call reviewer assignment.

DOCS_AGENT_WARP_API_KEY must be added as a GitHub Actions secret
in warpdotdev/docs — generate it from the Docs Agent page on
prod Oz: oz.warp.dev/agents/019eb332-2ee0-7417-8ecc-89260cf5b850

Co-Authored-By: Oz <oz-agent@warp.dev>

Author: dannyneira

.github/workflows/release-docs-update.yml

@@ -115,19 +115,15 @@ jobs:
               print("TRIGGER_CONTEXT_JSON", file=output)
           PY
 
-      # This workflow intentionally has no automatic push trigger yet.
-      # Enable automatic execution only after:
-      # 1. workflow_dispatch succeeds.
-      # 2. the channel-versions dispatch sender is tested.
-      # 3. required secrets, variables, and cross-repo permissions are configured.
-      # WARP_AGENT_PROFILE should be set to the Docs Agent on prod Oz (oz.warp.dev).
-      # That agent has DOCS_AGENT_GRAFANA_TOKEN configured for on-call reviewer assignment.
+      # DOCS_AGENT_WARP_API_KEY is an API key scoped to the Docs Agent on prod Oz
+      # (oz.warp.dev/agents/019eb332-2ee0-7417-8ecc-89260cf5b850). Running with
+      # that agent's key makes its per-agent secrets (e.g. DOCS_AGENT_GRAFANA_TOKEN
+      # for on-call reviewer assignment) available in the cloud run environment.
       - name: Run release docs update with Oz
         uses: warpdotdev/oz-agent-action@v1
         with:
           skill: warpdotdev/docs:release_updates
-          warp_api_key: ${{ secrets.WARP_API_KEY }}
-          profile: ${{ vars.WARP_AGENT_PROFILE || '' }}
+          warp_api_key: ${{ secrets.DOCS_AGENT_WARP_API_KEY }}
           prompt: |
             Run the release docs update workflow from the `release_updates` skill.