Add GitHub Actions CI workflow for build, lint, and test

.github/workflows/ci.yml

@@ -0,0 +1,85 @@
+name: CI
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  test:
+    name: Test and Lint
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.23.0'
+
+    - name: Cache Go modules
+      uses: actions/cache@v4
+      with:
+        path: |
+          ~/.cache/go-build
+          ~/go/pkg/mod
+        key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+        restore-keys: |
+          ${{ runner.os }}-go-
+
+    - name: Install dependencies
+      run: make deps
+
+    - name: Run checks (lint, vet, fmt-check, test)
+      run: make check
+
+    - name: Run security scan
+      run: make security
+      continue-on-error: true
+
+    - name: Run tests with coverage
+      run: make test-coverage
+
+    - name: Upload coverage reports
+      uses: actions/upload-artifact@v4
+      with:
+        name: coverage-report
+        path: coverage/
+
+  build:
+    name: Cross-platform Build
+    runs-on: ubuntu-latest
+    needs: test
+    strategy:
+      matrix:
+        target: [linux, darwin, windows]
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up Go
+      uses: actions/setup-go@v4
+      with:
+        go-version: '1.23.0'
+
+    - name: Cache Go modules
+      uses: actions/cache@v4
+      with:
+        path: |
+          ~/.cache/go-build
+          ~/go/pkg/mod
+        key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+        restore-keys: |
+          ${{ runner.os }}-go-
+
+    - name: Install dependencies
+      run: make deps
+
+    - name: Build for ${{ matrix.target }}
+      run: make build-${{ matrix.target }}
+
+    - name: Upload build artifacts
+      uses: actions/upload-artifact@v4
+      with:
+        name: build-${{ matrix.target }}
+        path: build/