fix(models): rank a version bump above a dated snapshot

[bsamek]

Problem

fireconnect model list fetched deepseek-v4p1-flash but never showed it as the newest model, and deepseek-flash-latest stayed pinned to the older deepseek-v4-flash-0731.

Root cause

stripVersionSegments folded release stamps into the version tuple, so:

• deepseek-v4p1-flash → [4, 1]
• deepseek-v4-flash-0731 → [4, 731]

731 > 1, so the dated v4 build won the "newest" comparison. newestModelsByFamily then dropped v4.1 from INDIVIDUAL MODELS, and ROUTER_SPEC_ALIASES/candidate lists kept the alias on 0731.

Fix

• stripVersionSegments now returns a separate date tuple for release stamps (0731, 0813, 20250731).
• New compareVersionKeys compares the version tuple first, using the date only as a tie-breaker:
  • deepseek-v4p1-flash [4,1] beats deepseek-v4-flash-0731 [4] + date [731]
  • deepseek-v4-flash-0731 still beats deepseek-v4-flash (dated build > undated base)
  • deepseek-v4-pro-0813 still beats deepseek-v4-pro
• Retargeted deepseek-flash-latest at deepseek-v4p1-flash (alias + candidate list) and added its static spec. The live catalog reports this model vision-capable, so its capability list is text, image.

Documented limitation: date stamps aren't normalized across formats, so an 8-digit YYYYMMDD value always compares above a 4-digit MMDD value. No family mixes formats today; a test pins the behavior.

Tests

• Added regression tests for version-bump-vs-date, date-vs-base, and the mixed-format behavior.
• Added alias-resolution coverage for a catalog holding both v4.1 and the dated v4 build.
• Updated Claude harness/CLI tests that assumed deepseek-flash-latest was text-only and labeled 0731.

npm test: 1820 tests, all pass except a pre-existing Azure/Foundry failure (codex on routes through the configured Foundry endpoint) that also fails on clean main.