feat(costs): add agent model breakdown, harden date validation, sync CostByProject type, fix quota threshold and tab-gated queries

- add byAgentModel endpoint and expandable per-agent model sub-rows in the spend tab
- validate date range inputs with isNaN + badRequest to return HTTP 400 on bad input
- move CostByProject from a local api/costs.ts definition into packages/shared types
- gate providerData query on mainTab === providers, consistent with weekData/windowData/quotaData
- fix byProject range filter from finishedAt to startedAt, consistent with byProvider runs query
- fix WHAM used_percent threshold from <= 1 to < 1 to avoid misclassifying 1% usage as 100%
- replace inline opacity style with tailwind bg-primary/85 class in ProviderQuotaCard
- reset expandedAgents set when company or date range changes
- sort agent model sub-rows by cost descending in ui memo

packages/shared/src/index.ts

@@ -133,7 +133,9 @@ export type {
   CostSummary,
   CostByAgent,
   CostByProviderModel,
+  CostByAgentModel,
   CostWindowSpendRow,
+  CostByProject,
   HeartbeatRun,
   HeartbeatRunEvent,
   AgentRuntimeState,

packages/shared/src/types/cost.ts

@@ -47,6 +47,17 @@ export interface CostByProviderModel {
   subscriptionOutputTokens: number;
 }
 
+/** per-agent breakdown by provider + model, for identifying token-hungry agents */
+export interface CostByAgentModel {
+  agentId: string;
+  agentName: string | null;
+  provider: string;
+  model: string;
+  costCents: number;
+  inputTokens: number;
+  outputTokens: number;
+}
+
 /** spend per provider for a fixed rolling time window */
 export interface CostWindowSpendRow {
   provider: string;
@@ -58,3 +69,12 @@ export interface CostWindowSpendRow {
   inputTokens: number;
   outputTokens: number;
 }
+
+/** cost attributed to a project via heartbeat run → activity log → issue → project chain */
+export interface CostByProject {
+  projectId: string | null;
+  projectName: string | null;
+  costCents: number;
+  inputTokens: number;
+  outputTokens: number;
+}

packages/shared/src/types/index.ts

@@ -46,7 +46,7 @@ export type {
   CompanySecret,
   SecretProviderDescriptor,
 } from "./secrets.js";
-export type { CostEvent, CostSummary, CostByAgent, CostByProviderModel, CostWindowSpendRow } from "./cost.js";
+export type { CostEvent, CostSummary, CostByAgent, CostByProviderModel, CostByAgentModel, CostWindowSpendRow, CostByProject } from "./cost.js";
 export type {
   HeartbeatRun,
   HeartbeatRunEvent,