fix(#31): catch version drift in CI, not at release time

Adds scripts/release/check-versions.sh and a `versions` CI job that runs
on every push/PR. Verifies:
- no per-crate Cargo.toml carries a literal version (must inherit the
  workspace version)
- npm/deepseek-tui/package.json matches the workspace version
- Cargo.lock is in sync with the manifests

Closes #31.

.github/workflows/ci.yml

@@ -11,6 +11,18 @@ env:
   RUSTFLAGS: -Dwarnings
 
 jobs:
+  versions:
+    name: Version drift
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - name: Check version drift
+        run: ./scripts/release/check-versions.sh
+
   lint:
     name: Lint
     runs-on: ubuntu-latest