fix(updater): suppress equal-version update prompts

[obazna]

Summary

• make the four-part product/local-build version authoritative for updater precedence
• treat Git hashes and dirty markers as display and artifact identity metadata only
• retain date ordering only for legacy three-part builds and preserve CalVer migration behavior

Reported regression

A clean release at 1.3.83.2 no longer appears newer than a local 1.3.83.2 dirty build merely because their commit hashes differ. A real 1.3.83.3 release still updates 1.3.83.2.

Verification

• UpdaterTests plus AppVersionTests: 51/51 passed
• Release build: 0 warnings, 0 errors
• full Avalonia suite: 1564/1565 passed; only the existing host-sensitive /dev/video0 normalization case failed
• behavior, integration, and test reviewers approve exact HEAD 8c5af6e

Manual acceptance

Rebuild and relaunch this branch, check against a signed release with the same four-part version and a different hash, and confirm it reports up to date instead of offering installation.