ci: publish to crates.io before GitHub release

Add cargo-publish job that runs in parallel with binary builds.
The release job now depends on [build-macos, build-linux, cargo-publish]
so the crate is always published to crates.io before the GitHub release
and binaries are attached.

Requires CARGO_REGISTRY_TOKEN secret in repo settings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -88,10 +88,36 @@ jobs:
           name: linux-binary
           path: dist/mcp-mt5-quant-linux-x64.tar.gz
 
+  # ── Cargo Publish ────────────────────────────────────────────────────────────
+
+  cargo-publish:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache Cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: cargo-publish-${{ hashFiles('Cargo.lock') }}
+          restore-keys: cargo-publish-
+
+      - name: Publish to crates.io
+        run: cargo publish --no-verify
+        env:
+          CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_REGISTRY_TOKEN }}
+
   # ── GitHub Release ───────────────────────────────────────────────────────────
 
   release:
-    needs: [build-macos, build-linux]
+    needs: [build-macos, build-linux, cargo-publish]
+
     runs-on: ubuntu-latest
     permissions:
       contents: write