[codex] fix damage calculator accuracy and lookup

[ChaseBianchi]

Summary

• Fix damage calculator handling for Vengeance, flat elemental damage, and off-weapon enhanced damage.
• Add committed damage regression snapshot tooling and tests to keep calculator output changes scoped.
• Remove season selection from direct character lookup and damage calculator URLs by resolving the season from returned character data.

Root cause

The calculator was undercounting several damage sources because some item/stat encodings were not being normalized into the same damage model buckets, and direct character lookup could resolve the wrong season through season fallback behavior.

Validation

• npm test -- --runInBand src/routes/routes.test.ts src/utils/damage-calculator.test.ts src/utils/damage-regression-snapshot.test.ts
• npm run build in api
• npm run build in web
• Manual QA on a local production build for legacy season query URLs and ChaseMeeee character/calculator flows.