chore: backlog cleanup — deps, CI, bot description, ops docs

- pin form-data/qs/tough-cookie via package.json overrides; clears 3 of 4
  Dependabot alerts (request SSRF risk-accepted, no upstream fix)
- add GitHub Actions CI (lint + syntax check) on push/PR
- add /settings and /setdayswarning to setMyCommands
- new npm run describe sets bot profile description via Bot API
- README: drop stale preview warning, add Operations section

.github/workflows/ci.yml

@@ -0,0 +1,21 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  verify:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+      - run: npm ci
+      - run: npm run lint
+      # Update find roots when adding new top-level JS dirs.
+      - name: Syntax check all JS
+        run: find api scripts src -name '*.js' -print0 | xargs -0 -n1 node --check