[simeonmiteff]

Summary

Prepare Quipu 0.5.1 with the workspace-diagnostics fix from #48. Bump the application and lockfile root versions, date the patch-release changelog, and add a pending acceptance record for the final Linux, Windows, and signed macOS packages.

After merge, the exact successful main CI commit will be tagged v0.5.1. The release/signing workflows will assemble an unpublished draft for platform testing.

Testing

• Rust 1.95: 319 tests passed, 1 ignored; formatting and Clippy passed.
• Frontend: 23 tests passed; production frontend/offline-documentation build passed.
• Release tooling: 2 public tests and 26 private signing/release tests passed; signing shell syntax checks passed.
• Linux UI harness unit tests: 9 passed.
• Third-party notices regenerated with no dependency changes.
• The maintainer manually verified the fix in the earlier 0.5.1-issue47.1 Debian test build; final 0.5.1 package acceptance remains pending.

Impact

• Application metadata identifies the release as 0.5.1.
• The release notes cover the parser/UTF-8 diagnostic-recovery fix.
• The acceptance checklist keeps final platform testing pending before publication.
• No runtime, dependency, IPC, or cache-format changes in this preparation commit.

Checklist

• I kept this pull request focused on one coherent change.
• I added or updated tests where behavior changed.
• I updated documentation and the changelog where appropriate.
• I used only sanitized, redistributable fixtures and screenshots.
• I reviewed the complete diff and can explain every submitted change.