docs(contracts): add docs.rs metadata and workflow verification

.github/workflows/contracts-docs.yml

@@ -0,0 +1,46 @@
+name: Contracts Docs
+
+on:
+  pull_request:
+    branches: [main]
+    paths:
+      - 'contracts/**'
+      - '.github/workflows/contracts-docs.yml'
+  push:
+    branches: [main]
+    paths:
+      - 'contracts/**'
+      - '.github/workflows/contracts-docs.yml'
+
+concurrency:
+  group: contracts-docs-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  docs:
+    name: Contracts Docs Build & Verification
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: contracts
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: wasm32-unknown-unknown
+
+      - name: Cache cargo artifacts
+        uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: contracts
+
+      - name: cargo doc (verify clean build with no broken links)
+        env:
+          RUSTDOCFLAGS: -D warnings
+        run: cargo doc --locked --no-deps --workspace