ci: cargo test + clippy + readme-lint on every PR

- cargo test and clippy run on all pushes
- readme-lint pulls from heraldstack-mcp and validates changed .md files on PRs
- fail fast: clippy treats warnings as errors

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

Author: Bryan Chasko

.github/workflows/ci.yml

@@ -0,0 +1,42 @@
+name: ci
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  test:
+    name: cargo test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+      - run: cargo test
+      - run: cargo clippy -- -D warnings
+      - run: cargo fmt --check
+
+  readme-lint:
+    name: readme-lint
+    runs-on: ubuntu-latest
+    if: github.event_name == 'pull_request'
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: Swatinem/rust-cache@v2
+        with:
+          workspaces: . -> target
+          cache-key: readme-lint
+      - name: build readme-lint
+        run: |
+          git clone https://github.com/BryanChasko/heraldstack-mcp.git /tmp/heraldstack-mcp
+          cargo build --release --manifest-path /tmp/heraldstack-mcp/tools/readme-lint/Cargo.toml
+      - uses: tj-actions/changed-files@v44
+        id: changed
+        with:
+          files: '**/*.md'
+      - if: steps.changed.outputs.any_changed == 'true'
+        run: /tmp/heraldstack-mcp/tools/readme-lint/target/release/readme-lint ${{ steps.changed.outputs.all_changed_files }}