chore: improve pretty collector format

[Nemo157]

I ended up doing a bit more refactoring of the pretty-printer to get it both testable and a format that I think is readable enough to merge. With the test you can step through the commits and see how the format changes with each.

I've targeted this for @arctic-alpaca's branch and propose we merge into that first, then merge it together as a whole.

[claude]

Change Summary

This PR refactors the ConsolePrettyExporter to improve formatting and testability. Key changes include converting the unit struct to a tuple struct wrapping an Output enum, reformatting log output with millisecond timestamps and padded columns, and adding comprehensive test coverage with an in-memory buffer variant.

Issues Found

I've identified 3 issues:

1. 🟡 Documentation inaccuracy (line 6): Doc comment states output goes to stdout, but implementation writes to stderr
2. 🟡 Error handling (line 205): Empty panic!() lacks descriptive message
3. 🟢 Minor formatting (line 82): Unnecessary trailing comma in writeln! macro

The refactoring successfully achieves its goals of improved formatting and testability. The test coverage is comprehensive with both boot-time and Unix timestamp scenarios.

[github-actions]

Deployment - Branch link	Commit link - 15419f6
user-manual preview	https://8d0020f2.user-manual-2bd.pages.dev
private-docs preview	https://e1294f1e.private-docs-3bh.pages.dev
veecle-telemetry-ui preview	https://8bf840f6.veecle-telemetry-ui.pages.dev

[codecov]

Codecov Report

❌ Patch coverage is 96.93878% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
veecle-telemetry/src/collector/pretty_exporter.rs	96.90%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!

[Nemo157]

/claude-review

[claude]

Change Summary

This PR refactors the ConsolePrettyExporter to improve formatting consistency and testability. The changes convert the unit struct to a tuple struct with a DEFAULT constant for static usage, extract formatting logic into a testable format_message helper function, improve log output formatting with millisecond timestamps and padded severity/time columns, fix string value display to use Debug formatting (adding quotes), and add comprehensive test coverage demonstrating both boot-time and Unix timestamp scenarios.

All previously identified issues have been addressed in the latest commits.

✅ Review complete - no new issues found

[HectorMRC]

I personally prefer naming this test by what it tests, but is not a blocker. Feel free to resolve.