feat: add reviewer github action

README.md

@@ -6,6 +6,34 @@ not contain review logic.
 
 ## Usage
 
+GitHub Actions:
+
+```yaml
+name: Postil review
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, ready_for_review]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  review:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: postil-dev/postil-reviewer@main
+        with:
+          api-key: ${{ secrets.OPENROUTER_API_KEY }}
+```
+
+The Action installs the `postil` binary from this repository revision, then runs
+`postil review` against the pull request.
+
+Local CLI:
+
 ```bash
 postil review --repo owner/repo --pr 123 --sha HEAD_SHA
 ```

action.yml

@@ -0,0 +1,63 @@
+name: 'Postil AI Review'
+description: 'AI pull-request reviewer for serious teams, open-source, zero-infra, fully auditable.'
+author: 'Postil'
+branding:
+  icon: 'git-pull-request'
+  color: 'blue'
+
+inputs:
+  api-key:
+    description: 'OpenRouter API key'
+    required: true
+  model:
+    description: 'OpenRouter model name'
+    required: false
+    default: 'moonshotai/kimi-k2.6'
+  fail-on:
+    description: 'Exit 1 when a finding meets this severity: info, warn, or error'
+    required: false
+    default: 'error'
+  no-inline:
+    description: 'Skip posting inline PR review comments'
+    required: false
+    default: 'false'
+  config-path:
+    description: 'Optional path to a configuration file'
+    required: false
+  github-token:
+    description: 'GitHub token for posting review comments'
+    required: false
+    default: '${{ github.token }}'
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Install Postil reviewer
+      shell: bash
+      run: cargo install --path "$GITHUB_ACTION_PATH" --locked --force
+    - name: Run Postil review
+      shell: bash
+      env:
+        GITHUB_TOKEN: ${{ inputs.github-token }}
+        OPENROUTER_API_KEY: ${{ inputs.api-key }}
+        REVIEW_MODEL: ${{ inputs.model }}
+        POSTIL_FAIL_ON: ${{ inputs.fail-on }}
+        POSTIL_CONFIG_PATH: ${{ inputs.config-path }}
+        POSTIL_NO_INLINE: ${{ inputs.no-inline }}
+      run: |
+        args=(review)
+        if [[ -n "$POSTIL_CONFIG_PATH" ]]; then
+          args+=(--config "$POSTIL_CONFIG_PATH")
+        fi
+        case "$POSTIL_NO_INLINE" in
+          true)
+            args+=(--no-inline)
+            ;;
+          false|"")
+            ;;
+          *)
+            echo "::error::no-inline must be 'true' or 'false'"
+            exit 1
+            ;;
+        esac
+        postil "${args[@]}"