ci: add CI checks and tag-triggered release workflow

Phase 2 of the 0.1.0 release prep, running on the GitHub mirror:
- ci.yml: frontend type-check/build, rustfmt gate, clippy (CPU-only) on
  windows-latest with pnpm + rust caching
- release.yml: v* tags build the NSIS installer via tauri-action and attach
  it to a draft GitHub Release with updater JSON; updater signing secrets
  referenced ahead of Phase 3
- both build --no-default-features: runners have no CUDA toolkit, and the
  shipped artifact must be the CPU/DirectML build

.github/workflows/ci.yml

@@ -0,0 +1,53 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    # windows-latest to match the release target — the ML crates (ort, candle)
+    # and the NSIS bundle only ever ship from Windows.
+    runs-on: windows-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+        with:
+          version: 11
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: pnpm
+
+      - name: Install frontend dependencies
+        run: pnpm install --frozen-lockfile
+
+      # tsc + vite build; also produces dist/ which tauri's build script expects
+      - name: Type-check and build frontend
+        run: pnpm build:vite
+
+      - name: Install Rust stable
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy, rustfmt
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: src-tauri
+
+      - name: Rustfmt
+        working-directory: src-tauri
+        run: cargo fmt --check
+
+      # Default features only — candle-cuda must never be enabled in CI.
+      - name: Clippy
+        working-directory: src-tauri
+        run: cargo clippy --all-targets --locked