Post a comment when lifecycle labels are applied to issues (#25665)

When lifecycle labels (needs-info, needs-repro, invalid, stale, autoclose)
are applied to an issue, the author currently only sees a label change with
no explanation. They then get a closing comment days later without ever
being nudged to respond.

Add a GitHub Actions workflow that triggers on issues.labeled and runs a
new lifecycle-comment.ts script to post a comment explaining what's needed
and how long before auto-close.

Extract lifecycle config (labels, timeouts, close reasons, nudge messages)
into a shared issue-lifecycle.ts so the sweep script and comment script
stay in sync. Previously the timeouts were duplicated between the sweep
script and the comment messages.

- needs-info: asks for version, OS, error messages
- needs-repro: asks for steps to trigger the issue
- invalid: links to the Claude Code repo and Anthropic support
- stale/autoclose: explains inactivity auto-close

The script no-ops for non-lifecycle labels, so the workflow fires on every
label event and lets the script decide — single source of truth.

## Test plan

Dry-run all labels locally:
GITHUB_REPOSITORY=anthropics/claude-code LABEL=needs-info ISSUE_NUMBER=12345 bun run scripts/lifecycle-comment.ts --dry-run
GITHUB_REPOSITORY=anthropics/claude-code LABEL=needs-repro ISSUE_NUMBER=12345 bun run scripts/lifecycle-comment.ts --dry-run
GITHUB_REPOSITORY=anthropics/claude-code LABEL=invalid ISSUE_NUMBER=12345 bun run scripts/lifecycle-comment.ts --dry-run
GITHUB_REPOSITORY=anthropics/claude-code LABEL=stale ISSUE_NUMBER=12345 bun run scripts/lifecycle-comment.ts --dry-run
GITHUB_REPOSITORY=anthropics/claude-code LABEL=autoclose ISSUE_NUMBER=12345 bun run scripts/lifecycle-comment.ts --dry-run

Verified sweep.ts still works:
GITHUB_TOKEN=$(gh auth token) GITHUB_REPOSITORY_OWNER=anthropics GITHUB_REPOSITORY_NAME=claude-code bun run scripts/sweep.ts --dry-run

.github/workflows/issue-lifecycle-comment.yml

@@ -0,0 +1,27 @@
+name: "Issue Lifecycle Comment"
+
+on:
+  issues:
+    types: [labeled]
+
+permissions:
+  issues: write
+
+jobs:
+  comment:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Post lifecycle comment
+        run: bun run scripts/lifecycle-comment.ts
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          LABEL: ${{ github.event.label.name }}
+          ISSUE_NUMBER: ${{ github.event.issue.number }}