feat(agent): support Responses steering and project-aware tools

Use the dedicated TJWATER_AGENT_URL and Responses stream protocol. Keep running
turns active while users steer or queue follow-ups and edit pending delivery.
Refresh the model catalog before generation and preserve approval mode selection.

Integrate scoped investigation messaging/presentation, geographic place selection,
current Agent composer styles and supporting workbench contracts.

Validation: 77 focused Vitest checks, 21 browser cases, lint, typecheck and
production build. Preserve direct Server/Agent routing and project authentication.

src/features/agent/api/agent-messages.ts

@@ -0,0 +1,21 @@
+import { z } from "zod";
+
+export const agentMessageSchema = z.object({
+  message_id: z.string().min(1),
+  task_id: z.string().min(1),
+  run_id: z.string().min(1),
+  source_session_id: z.string().min(1),
+  target_session_id: z.string().min(1).nullable(),
+  direction: z.enum(["to_task", "to_chat"]),
+  text: z.string(),
+  status: z.enum(["pending", "enqueued", "delivered", "failed"]),
+  in_reply_to: z.string().nullable(),
+  created_at: z.string(),
+  failure_detail: z.string().nullable().optional()
+});
+export const agentMessagePageSchema = z.object({
+  items: z.array(agentMessageSchema),
+  next_cursor: z.string().nullable()
+});
+export type AgentMailboxMessage = z.infer<typeof agentMessageSchema>;
+export type AgentMessagePage = z.infer<typeof agentMessagePageSchema>;