fix(token-usage): profile-aware config tier, uniform speed_inferred, version guard

Three review findings on the extraction layer:

- The config.toml fallback used ccusage's table-blind line scan, so a
  `service_tier = "fast"` inside an INACTIVE [profiles.*] table marked
  every rollout under the codex home fast, billing unmarked entries at
  the model's fast multiplier. It now parses the file properly (toml
  crate, like streams::model_extraction): the active profile's tier
  wins, else the top-level key — a documented deviation from ccusage's
  scan.

- Unmarked Claude entries hardcoded speed_inferred=false while the
  identical condition on Codex reports true, making the wire flag
  uninterpretable across tools. The flag means "tier not recorded in
  the transcript" and Claude now reports it that way.

- migrate() had no guard against a database written by a newer binary.
  Migrations are destructive from v3 on, so a downgraded daemon would
  open fine and then fail every pass at runtime on missing columns;
  it now fails closed at open with an actionable message.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>