replit2api2

feat(api-server): backfill Anthropic-canonical headers + fill response usage/stop_sequence

fix(api-server): preserve thinking-effort intent on 4-7+ + add sanitiser kill-switch

fix(api-server): make thinking/output_config sanitiser model-aware

fix(api-server): strip output_config/output_format before forwarding to Vertex

fix: restore real Anthropic model ids (claude-opus-4-7/4-6, sonnet-4-6, haiku-4-5)