ci: install knip (Tier-2 — dead code + unused deps) (#127)

Finds unused exports, unreferenced files, and uninstalled deps in
TypeScript codebases. Replaces ts-prune (unmaintained). Warn-only
initially.

Co-authored-by: Claude <claude@anthropic.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: mastermanas805

.github/workflows/knip.yml

@@ -0,0 +1,23 @@
+name: knip (dead code + unused deps)
+
+on:
+  push:
+    branches: [master, main]
+  pull_request:
+    branches: [master, main]
+
+permissions:
+  contents: read
+
+jobs:
+  knip:
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: npm
+      - run: npm ci
+      - run: npx knip --no-exit-code  # warn-only initially; remove --no-exit-code once baseline is clean