docs(cla): add Contributor License Agreement and GitHub Actions workflow

.github/workflows/cla.yml

@@ -0,0 +1,41 @@
+name: CLA Assistant
+
+on:
+  issue_comment:
+    types: [created]
+  pull_request_target:
+    types: [opened, closed, synchronize]
+
+permissions:
+  actions: write
+  contents: write
+  pull-requests: write
+  statuses: write
+
+jobs:
+  cla:
+    runs-on: ubuntu-latest
+    steps:
+      - name: CLA Assistant
+        if: (github.event.comment.body == 'recheck' || github.event.comment.body == 'I have read the CLA Document and I hereby sign the CLA') || github.event_name == 'pull_request_target'
+        uses: contributor-assistant/github-action@v2.6.1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          path-to-signatures: 'signatures/cla.json'
+          path-to-document: 'https://github.com/code-yeongyu/oh-my-opencode/blob/master/CLA.md'
+          branch: 'main'
+          allowlist: bot*,dependabot*,github-actions*,*[bot]
+          custom-notsigned-prcomment: |
+            Thank you for your contribution! Before we can merge this PR, we need you to sign our [Contributor License Agreement (CLA)](https://github.com/code-yeongyu/oh-my-opencode/blob/master/CLA.md).
+            
+            **To sign the CLA**, please comment on this PR with:
+            ```
+            I have read the CLA Document and I hereby sign the CLA
+            ```
+            
+            This is a one-time requirement. Once signed, all your future contributions will be automatically accepted.
+          custom-pr-sign-comment: 'I have read the CLA Document and I hereby sign the CLA'
+          custom-allsigned-prcomment: |
+            All contributors have signed the CLA. Thank you! ✅
+          lock-pullrequest-aftermerge: false