Use getLegacyKeyTitle for backward-compatible key lookup

[Copilot]

Description

The getLegacyKeyTitle function was defined but never called, preventing cleanup of SSH keys created with the old format (cassh-{connID}) when users upgrade to the new format (cassh-{connID}@{hostname}).

Changes:

• findGitHubKeyIDByTitle: Extracts connection ID from new-format titles, generates legacy title via getLegacyKeyTitle(), and checks both formats in a single pass with exact matching
• rotatePersonalGitHubSSH: Adds fallback lookup when GitHubKeyID is unset (migration scenario), attempts to find and delete keys using both title formats before generating new key

// Now handles both formats in one iteration
if keyTitle == title {
    return keyID  // New format: cassh-personal-123@MacBook-Pro
}
if legacyTitle != "" && keyTitle == legacyTitle {
    return keyID  // Legacy format: cassh-personal-123
}

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 not work as expected)
• Documentation update
• Refactoring (no functional changes)

Related Issues

Addresses feedback from #7 (comment r2608119934)

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual testing

Test environment:

• OS: macOS (darwin-specific code)
• Go version: 1.24.11

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Security Considerations

• This PR does not introduce any security concerns
• I have considered the security implications and addressed them

CodeQL analysis: 0 alerts

Screenshots (if applicable)

N/A

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[Copilot]

Pull request overview

This PR fixes a bug where the getLegacyKeyTitle function was defined but never used, preventing cleanup of SSH keys created with the legacy format (cassh-{connID}) when users upgrade to the new format (cassh-{connID}@{hostname}). The fix enables backward-compatible key lookup to handle migration scenarios smoothly.

Key Changes:

• Enhanced findGitHubKeyIDByTitle to extract connection IDs from new-format titles and check both new and legacy title formats with exact matching
• Added fallback lookup in rotatePersonalGitHubSSH for migration scenarios where GitHubKeyID is unset, enabling discovery and cleanup of keys using either title format

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[shawntz]

fizzy