<!-- CURSOR_SUMMARY -->
> [!NOTE]
> Introduces contributor licensing and automated CLA enforcement.
> 
> - Adds `CLA.md` (individual agreement) and documents FSL licensing for
`src/pro` (`CONTRIBUTING.md`, `src/pro/CONTRIBUTING.md`)
> - New GitHub Actions workflow `/.github/workflows/cla.yml` using
`contributor-assistant/github-action@v2.6.1` on `pull_request_target`
and `issue_comment`
> - Stores signatures at `signatures/version1/cla.json` on branch `cla`
and updates PR status; supports signing via comment or `recheck`
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
5706a5ace13aabd8e8e83fdd071d65f7fc40500f. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Add a Contributor License Agreement and a GitHub Action that blocks PRs
until all authors sign the CLA. Also clarifies that contributions in
src/pro are licensed under FSL.

- **New Features**
  - Added CLA.md for individual contributors.
- Enabled CLA Assistant on pull_request_target and issue_comment events.
- Stores signatures at signatures/version1/cla.json on the cla branch
and updates PR status.
  - Supports “recheck” and signing via comment.
  - Documented FSL licensing for src/pro contributions.

- **Migration**
- Ensure the cla branch is not protected, or change the action’s target
branch.
  - Optionally configure an allowlist to fit your org.
- If storing signatures remotely, add the PERSONAL_ACCESS_TOKEN secret.
- Contributors sign by commenting: “I have read the CLA Document and I
hereby sign the CLA”.

<sup>Written for commit 5706a5ace13aabd8e8e83fdd071d65f7fc40500f.
Summary will update on new commits.</sup>

<!-- End of auto-generated description by cubic. -->