[Task 07] Wire non-streaming chat completions

[lubobill1990]

Task 07 — Wire non-streaming chat completions

Depends on: 03, 04, 06
Unblocks: 11

Goal

The simplest end-to-end recorder integration: a non-streaming OpenAI
chat-completions request results in exactly one usage_events row with
populated token counts and price snapshots.

Scope

In src/services/copilot/create-chat-completions.ts and
src/routes/chat-completions/handler.ts:

• Capture tStart = Date.now() at the beginning of the handler.
• After a successful non-streaming response, call recordUsage with:
  • usage = normalizeOpenAIFinal(response.usage)
  • endpoint = 'chat.completions'
  • upstreamFormat = 'openai'
  • isStreaming = false
  • status = 'ok'
  • durationMs = Date.now() - tStart
  • requestId = response.id
  • isInternal = c.req.header('x-internal-pricing-sync') === '1'
• On thrown error before recordUsage: best-effort write a status = 'error'
  event with zero usage. Skip on missing model.

Streaming branch: untouched in this task (task 08 owns it).

Definition of Done

• Manual smoke: send a non-streaming request via curl; observe 1 row in
  usage_events and 1 / +1 in usage_daily.
• Repeat with two accounts; verify account_name reflects the chosen
  account.
• No regression in the streaming path.
• isInternal request (header set) does not produce a row.

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• Source: docs/tasks/07-wire-nonstreaming-chat.md
• Design: docs/design/
• Phase: wiring
• Depends on tasks: 3, 4, 6