Context

`src/infra/session-cost-usage.*` (1,586 lines) reads JSONL session transcripts post-hoc to compute cost summaries, model usage stats, and latency metrics. This is analytics/billing UX that reads local artifacts — it doesn't route through sessions, channels, or gateway. It's a platform feature for the consumer dashboard.

Found during MBP deep dive audit of `src/infra/`.

Scope

Delete session-cost-usage files (3 files, 1,586 lines):

• `session-cost-usage.ts` (999 lines)
• `session-cost-usage.types.ts` (158 lines)
• `session-cost-usage.test.ts` (429 lines)

Clean up callers:

• `/usage` command in auto-reply — remove cost summary section or stub
• Status commands that display session cost — remove the section

Acceptance Criteria

• `grep -r "session-cost-usage" src/` returns nothing
• Build passes
• Tests pass

Size

~1,586 lines removed.