Pass RUNTIME_TRIAGE_TOKEN to GitHub tools for cross-repo reads

The agent's GitHub MCP tools need the PAT to read files from
copilot-agent-runtime. The github-token under safe-outputs only
applies to safe output jobs, not the agent itself.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: patniko

.github/workflows/cross-repo-issue-analysis.lock.yml

@@ -16,6 +16,7 @@ permissions:
 tools:
   github:
     toolsets: [default]
+    github-token: ${{ secrets.RUNTIME_TRIAGE_TOKEN }}
   edit:
 safe-outputs:
   github-token: ${{ secrets.RUNTIME_TRIAGE_TOKEN }}