Remove oncall triage workflow and commands

Removes the automated action that adds the "oncall" label to issues,
along with its associated slash commands.

https://claude.ai/code/session_01KdEmZZ4sqZT4d9xJm4qbnp

.github/workflows/oncall-triage.yml

@@ -1,34 +0,0 @@
-name: Oncall Issue Triage
-description: Automatically identify and label critical blocking issues requiring oncall attention
-on:
-  push:
-    branches:
-      - add-oncall-triage-workflow  # Temporary: for testing only
-  schedule:
-    # Run every 6 hours
-    - cron: '0 */6 * * *'
-  workflow_dispatch: # Allow manual trigger
-
-jobs:
-  oncall-triage:
-    runs-on: ubuntu-latest
-    timeout-minutes: 25
-    permissions:
-      contents: read
-      issues: write
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-
-      - name: Run Claude Code for Oncall Triage
-        timeout-minutes: 20
-        uses: anthropics/claude-code-action@v1
-        env:
-          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-          GH_REPO: ${{ github.repository }}
-        with:
-          github_token: ${{ secrets.GITHUB_TOKEN }}
-          allowed_non_write_users: "*"
-          prompt: "/oncall-triage-ci REPO: ${{ github.repository }}"
-          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}