test(ssh): improve SSH proxy test coverage

[fabiovincenzi]

Description

Add tests to improve SSH proxy coverage, focusing on the four modules with the most gaps:

• server.ts: push flow (no-op detection, security chain integration, pack size/chunk limits, timeout), path validation, auth edge cases, debug mode
• GitProtocol.ts: happy paths for all 4 exported functions
• sshInternals.ts: all exported functions with failure modes and error messages
• AgentForwarding.ts : CHANNEL_OPEN_CONFIRMATION handler, lock recovery

Related Issue

Resolves #1586

Checklist

General

• I have read the CONTRIBUTING.md guidelines
• Commit messages follow Conventional Commits format
• I have a FINOS CLA on file

Documentation

• Documentation has been added/updated for any new features (N/A — test-only changes)

Configuration

• If configuration schema (config.schema.json) was modified (N/A — no config changes)

Tests

• Tests have been added/updated for new functionality
• Unit tests pass (npm test)
• Linting and formatting pass (npm run lint and npm run format:check)
• Type checks pass (npm run check-types)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.41%. Comparing base (d571a17) to head (e249ac5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1628      +/-   ##
==========================================
+ Coverage   86.31%   90.41%   +4.09%     
==========================================
  Files          87       87              
  Lines        8661     8661              
  Branches     1514     1603      +89     
==========================================
+ Hits         7476     7831     +355     
+ Misses       1155      799     -356     
- Partials       30       31       +1     

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[jescalada]

Excellent work on getting our coverage back to standard! 🎉

Just a few minor comments/suggestions from me. I'd like to merge this ASAP for the coverage increase, despite conflicts with the Vitest 4 upgrade PR #1564. I'm happy to deal with failing tests later 🙂

[jescalada]

LGTM! 👍🏼