Rename the admin-managed SDK resource from `ChatModelConfig` to
`ChatModel`. Rename catalog entries from `ChatModel` to
`ChatModelCatalogEntry` and replace `ChatModelsResponse` with
`ChatModelAvailabilityResponse`.
API routes and JSON fields do not change. Experimental SDK and OpenAPI
schema names do change.
Depends on #27957
_This pull request description was generated by Coder Agents._
## Stack Context
This stack makes AI Gateway data and budgets the source of truth for AI
spend controls.
1. Re-back the per-chat cost endpoint with AI Gateway data (#27328,
merged).
2. Remove native chat usage limits (#27329, merged).
3. **This PR, now based on `main`:** remove native chat cost tracking
and its dedicated admin UI.
## Summary
Removes native per-message price calculation, model pricing fields, cost
persistence, aggregate cost queries, and admin cost API types. It also
deletes the Analytics and Spend pages plus their legacy redirects. The
AI Gateway-backed per-chat cost row and compact budget indicators
remain.
The spend documentation is renamed to `spend-management.md` and updated
for the remaining surfaces, group budget APIs, CSV export, upgrade
handling for native pricing and cost history, and the absence of a
deployment-wide spend dashboard. The per-chat cost API documents that
data follows AI Gateway retention and reports zero after all matching
requests are purged.
No schema is dropped in this release. `chat_messages.total_cost_micros`
remains nullable and unwritten so replicas from the previous release can
continue inserting messages during rolling upgrades. #27600 tracks
removal after the compatibility window.
> Mux prepared this PR on Mike's behalf.
Ethan