[Task 09] Wire embeddings

[lubobill1990]

Task 09 — Wire embeddings

Depends on: 06
Unblocks: 11

Goal

Embedding calls record usage_events rows with endpoint = 'embeddings'.

Scope

In src/services/copilot/create-embeddings.ts and the embeddings route
handler:

• recordUsage with:
  • endpoint = 'embeddings'
  • upstreamFormat = 'openai'
  • isStreaming = false
  • usage = normalizeEmbeddings(response.usage)
• Output / reasoning / cached input columns are zero by definition.

Pricing for embedding models reuses model_pricing.input_per_mtok. No new
columns.

Definition of Done

• Manual smoke: a /v1/embeddings request produces a row with
  endpoint = 'embeddings', output_tokens = 0, and input_tokens > 0.
• usage_daily aggregates separately from chat.completions for the
  same model (different endpoint PK component).

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• Source: docs/tasks/09-wire-embeddings.md
• Design: docs/design/
• Phase: wiring
• Depends on tasks: 6