Initial commit: krust - container image build tool for Rust

krust builds container images for Rust applications without Docker:
- Builds static binaries using musl libc
- Creates minimal OCI container images
- Pushes to any OCI-compliant registry
- Outputs digest to stdout for composability

Inspired by ko.build for Go applications.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.github/workflows/ci.yml

@@ -0,0 +1,82 @@
+name: CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  test:
+    name: Test
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
+        rust: [stable, beta]
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Rust
+      uses: dtolnay/rust-toolchain@master
+      with:
+        toolchain: ${{ matrix.rust }}
+    - name: Cache cargo registry
+      uses: actions/cache@v4
+      with:
+        path: ~/.cargo/registry
+        key: ${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+    - name: Cache cargo index
+      uses: actions/cache@v4
+      with:
+        path: ~/.cargo/git
+        key: ${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
+    - name: Cache cargo build
+      uses: actions/cache@v4
+      with:
+        path: target
+        key: ${{ runner.os }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
+    - name: Build
+      run: cargo build --verbose
+    - name: Run unit tests
+      run: cargo test --verbose
+    - name: Run e2e tests
+      run: cargo test --test '*' --verbose
+
+  fmt:
+    name: Rustfmt
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Rust
+      uses: dtolnay/rust-toolchain@stable
+      with:
+        components: rustfmt
+    - name: Check formatting
+      run: cargo fmt -- --check
+
+  clippy:
+    name: Clippy
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Rust
+      uses: dtolnay/rust-toolchain@stable
+      with:
+        components: clippy
+    - name: Run clippy
+      run: cargo clippy -- -D warnings
+
+  coverage:
+    name: Code coverage
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - name: Install Rust
+      uses: dtolnay/rust-toolchain@stable
+    - name: Install cargo-tarpaulin
+      run: cargo install cargo-tarpaulin
+    - name: Generate code coverage
+      run: cargo tarpaulin --verbose --workspace