feat(tui): add download progress UI and chunked file download

[Zayan-Mohamed]

• Add download message types and downloadState to track progress, speed and cancellation
• Implement initiateDownload to download files in chunks over the tunnel and emit progress / error / cancel messages
• Add progress overlay UI (renderDownloadProgress) with progress bar, speed and cancel hint
• Prevent UI interactions during active downloads and add ESC key to cancel
• Keep backward compatibility: downloadFile now routes to the new flow after stat
• Update styles and helper rendering for progress and status

Files:

• browser.go

Signed-off-by: Zayan-Mohamed itsm.zayan@gmail.com

Pull Request

Description

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Code refactoring
• CI/CD changes

Related Issues

Fixes #

Changes Made

Testing

• Unit tests pass (make test)
• Integration tests pass (if applicable)
• Manual testing completed
• Tested on multiple platforms (list them below)

Tested On

• Linux
• macOS
• Windows

Security Considerations

• This change does not weaken encryption, privacy, or isolation
• No sensitive data is logged or exposed
• Input validation is properly implemented
• No new attack vectors are introduced

Security Impact:

Documentation

• Documentation has been updated (if needed)
• Code comments added for complex logic
• CHANGELOG.md updated (for user-facing changes)

Checklist

• My code follows the project's code style
• 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 or errors
• 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

Screenshots (if applicable)

Additional Notes

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By submitting this PR, I confirm that:

• I have read and agree to the Contributing Guidelines
• My contribution is made under the project's MIT License
• I understand that security is paramount and this change maintains Orb's security standards

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 0% with 174 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/tui/browser.go	0.00%	174 Missing ⚠️

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