feat(allowlist): add matlab support

[GenosseFlosse]

Description

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactoring (no functional changes)
• Documentation update
• CI / Build / Tooling

How Has This Been Tested?

• make test passes locally
• Manual testing (describe below)

Checklist

• My code follows the project's coding style (go fmt, go vet)
• I have performed a self-review of my code
• I have added tests that prove my fix is effective or my feature works
• New and existing unit tests pass locally with my changes
• I have updated the documentation accordingly (if applicable)
• I have signed the CLA

Related Issues

[CLAassistant]

All committers have signed the CLA.

[github-actions]

✅ OpenCodeReview: No comments generated. Looks good to me.

[lizhengfeng101]

Thanks for the contribution — the MATLAB rule doc itself is excellent and very thorough!

One concern before merging: the .m extension is shared between MATLAB and Objective-C. This PR maps all **/*.m files to matlab.md, which means Objective-C files (e.g. ios/ViewController.m, AppDelegate.m) will receive MATLAB-specific review feedback — clearly incorrect for those files.

The test change confirms this: ios/ViewController.m was removed from the "fallback to default" test because it now matches the MATLAB rule.

Possible approaches

1. Path-based heuristics — put ObjC-specific glob patterns (e.g. **/{ios,macos,tvos,watchos,Pods,Classes}/**/*.m) before **/*.m in system_rules.json, leveraging "first match wins" order. Downside: incomplete coverage, maintenance burden.

2. Content-based detection — sniff the first line of the file (function → MATLAB, #import/#include → ObjC). Downside: requires changes to the Resolve interface which currently only takes a path.

3. Accept the limitation — document that .m defaults to MATLAB and ObjC projects should use a project-level .opencodereview/rule.json to override. Simplest, but shifts burden to ObjC users.

Minor formatting issues in system_rules.json

• Trailing space on the "**/*.bicep": "bicep.md", line
• The new "**/*.m" entry uses a tab for indentation, while the rest of the file uses 4 spaces

Would love to hear your thoughts on how you'd like to handle the extension ambiguity. Happy to discuss further!