ci: add GitHub Actions workflows; drop obsolete build scripts

Two workflows:

  .github/workflows/ci.yml   — runs on push/PR to main and memory-refactor
    - cargo fmt --check (enforced)
    - cargo clippy -D warnings (enforced)
    - cargo build --locked
    - cargo test --lib --locked

  .github/workflows/release.yml — runs on tag push `v*` (or manual dispatch)
    - Matrix builds on native runners for four targets:
        aarch64-apple-darwin       → macos-latest (Apple Silicon runner)
        x86_64-apple-darwin        → macos-13 (last Intel runner image)
        x86_64-unknown-linux-gnu   → ubuntu-latest
        aarch64-unknown-linux-gnu  → ubuntu-24.04-arm (free public runner)
    - Each job packages ling-mem-<target>.tar.gz + .sha256 + README + LICENSE
    - Artifacts uploaded, then a single publish job creates the GitHub
      Release with all four tarballs + combined SHA256SUMS.txt
    - Uses Swatinem/rust-cache (keyed per target) to reuse the LanceDB
      dep tree between runs.

Dropped: scripts/ and Dockerfile.linux (all references `backend/` and
`frontend/` which no longer exist). Local-dev builds just run
`cargo build`; CI handles the release distribution now.

Incidental: rustc/clippy cleanup to get -D warnings passing:
  - Origin now #[derive(Default)] with #[default] on Derived (was
    manual Default impl).
  - Doc list in Origin fixed to have a blank line before the standalone
    paragraph (clippy's doc_lazy_continuation lint).

60 tests still passing. cargo fmt + clippy + test all clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: linggen

.github/workflows/ci.yml

@@ -0,0 +1,39 @@
+name: ci
+
+on:
+  push:
+    branches: [main, memory-refactor]
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: "-D warnings"
+
+jobs:
+  test:
+    name: build + test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy, rustfmt
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          # The LanceDB dep tree is big; cache shared across matrix jobs.
+          shared-key: ling-mem
+
+      - name: cargo fmt
+        run: cargo fmt --all -- --check
+
+      - name: cargo clippy
+        # Warnings-as-errors is handled by RUSTFLAGS above; also deny clippy.
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: cargo build
+        run: cargo build --locked
+
+      - name: cargo test
+        run: cargo test --lib --locked

.github/workflows/release.yml

@@ -0,0 +1,104 @@
+name: release
+
+on:
+  push:
+    tags: ['v*']
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Tag to build (must already exist)'
+        required: true
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build:
+    name: build (${{ matrix.target }})
+    runs-on: ${{ matrix.runner }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - target: aarch64-apple-darwin
+            runner: macos-latest     # GitHub's macOS runners are now ARM64 by default.
+          - target: x86_64-apple-darwin
+            runner: macos-13         # Last Intel macOS runner image.
+          - target: x86_64-unknown-linux-gnu
+            runner: ubuntu-latest
+          - target: aarch64-unknown-linux-gnu
+            runner: ubuntu-24.04-arm # Free for public repos since Jan 2025.
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.inputs.tag || github.ref }}
+
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: ${{ matrix.target }}
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          key: release-${{ matrix.target }}
+
+      - name: build release binary
+        run: cargo build --release --target ${{ matrix.target }} --locked --bin ling-mem
+
+      - name: package tarball
+        shell: bash
+        run: |
+          set -euo pipefail
+          BIN_DIR="target/${{ matrix.target }}/release"
+          STAGING="$(mktemp -d)"
+          cp "$BIN_DIR/ling-mem" "$STAGING/"
+          cp README.md LICENSE "$STAGING/" || true
+          TARBALL="ling-mem-${{ matrix.target }}.tar.gz"
+          (cd "$STAGING" && tar czf "$GITHUB_WORKSPACE/$TARBALL" .)
+          # sha256 checksum for the release page
+          if command -v shasum >/dev/null; then
+            shasum -a 256 "$TARBALL" > "$TARBALL.sha256"
+          else
+            sha256sum "$TARBALL" > "$TARBALL.sha256"
+          fi
+          ls -la "$TARBALL"*
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: ling-mem-${{ matrix.target }}
+          path: |
+            ling-mem-${{ matrix.target }}.tar.gz
+            ling-mem-${{ matrix.target }}.tar.gz.sha256
+
+  publish:
+    name: publish release
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.inputs.tag || github.ref }}
+
+      - uses: actions/download-artifact@v4
+        with:
+          pattern: ling-mem-*
+          path: artifacts
+          merge-multiple: true
+
+      - name: compose combined checksums
+        run: |
+          set -euo pipefail
+          cd artifacts
+          cat *.sha256 > SHA256SUMS.txt
+          ls -la
+
+      - name: publish GitHub release
+        uses: softprops/action-gh-release@v2
+        with:
+          tag_name: ${{ github.event.inputs.tag || github.ref_name }}
+          draft: false
+          generate_release_notes: true
+          files: |
+            artifacts/*.tar.gz
+            artifacts/SHA256SUMS.txt