feat(observability): add request-level Discovery routing trace

drizzle/0111_happy_mauler.sql

@@ -0,0 +1,41 @@
+ALTER TABLE "message_request" ADD COLUMN "routing_trace" jsonb;
+
+-- Routing trace finalization is observability-only. Restrict the ledger trigger
+-- to columns that can actually change its projection so trace-only patches do
+-- not rewrite accounting rows.
+DROP TRIGGER IF EXISTS trg_upsert_usage_ledger ON message_request;
+
+CREATE TRIGGER trg_upsert_usage_ledger
+AFTER INSERT OR UPDATE OF
+  blocked_by,
+  status_code,
+  error_message,
+  provider_chain,
+  actual_response_model,
+  endpoint,
+  provider_id,
+  user_id,
+  "key",
+  model,
+  original_model,
+  api_type,
+  session_id,
+  cost_usd,
+  cost_multiplier,
+  group_cost_multiplier,
+  input_tokens,
+  output_tokens,
+  cache_creation_input_tokens,
+  cache_read_input_tokens,
+  cache_creation_5m_input_tokens,
+  cache_creation_1h_input_tokens,
+  cache_ttl_applied,
+  context_1m_applied,
+  swap_cache_ttl_applied,
+  duration_ms,
+  ttfb_ms,
+  client_ip,
+  created_at
+ON message_request
+FOR EACH ROW
+EXECUTE FUNCTION fn_upsert_usage_ledger();