fix: Match ccusage 20.0.9 cost calc; persist parse cache

ccusage moved 18.0.11 -> native-binary 20.0.9, changing three things we
now mirror:
- 1-hour cache writes bill at 2x base input (was a flat 5m rate). This is
  the dominant cost component for Claude Code (~90-99% of cache is 1h TTL),
  so the old calc undercounted "today's cost" by ~9%.
- Row dedup switched first-wins -> max-output-wins: a message is written
  twice (partial stream snapshot + final), same msgid:requestId with
  identical input/cache but growing output_tokens; keep the complete copy.
- ccusage became multi-provider (Codex/Kimi/...); we stay Claude-only.

Verified: Tools/recalc_cost.swift matches ccusage 20.0.9 to the cent across
30 days; verify_cost.sh excludes the in-progress day and filters Claude-only.

Also fixes a pre-existing SAVE failure: a .infinity timestamp sentinel made
JSONEncoder reject the whole envelope, so the parse cache never persisted
and every refresh did a full ~8s re-parse. Now finite; cache schema V2->V3.