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.

tests/browser/agent-answer-ui.e2e.ts

@@ -1,3 +1,4 @@
+import { responsesFixture } from "./support/responses-fixture";
 import { expect, test } from "@playwright/test";
 import { mockAgentApi } from "./support/mock-agent-api";
 import { mockWorkbenchContext } from "./support/mock-workbench-context";
@@ -99,7 +100,7 @@ for (const width of [1440, 375, 320]) {
         data: { content: "仍需用户补充现场核验资料。", ui_block_ids: ["pressure"] }
       }
     ];
-    await page.route("**/api/v1/agent/chat/session/browser-session-1", async (route) => {
+    await page.route("**/api/v1/session/browser-session-1", async (route) => {
       if (route.request().method() !== "GET") return route.fallback();
       await route.fulfill({
         headers: { "Access-Control-Allow-Origin": "*" },
@@ -121,16 +122,16 @@ for (const width of [1440, 375, 320]) {
       });
     });
     const prompts: string[] = [];
-    await page.route("**/api/v1/agent/chat/stream", async (route) => {
+    await page.route("**/api/v1/responses", async (route) => {
       if (route.request().method() === "OPTIONS") return route.fallback();
       const body = route.request().postDataJSON() as {
-        messages: Array<{ role: string; parts: Array<{ type: string; text?: string }> }>;
+        input: Array<{ role: string; content: Array<{ type: string; text?: string }> }>;
       };
       const text =
-        body.messages
+        body.input
           .filter((m) => m.role === "user")
           .at(-1)
-          ?.parts.filter((p) => p.type === "text")
+          ?.content.filter((p) => p.type === "input_text")
           .map((p) => p.text)
           .join("") ?? "";
       prompts.push(text);
@@ -160,9 +161,9 @@ for (const width of [1440, 375, 320]) {
         headers: {
           "Access-Control-Allow-Origin": "*",
           "Content-Type": "text/event-stream",
-          "X-Vercel-AI-UI-Message-Stream": "v1"
+          "Cache-Control": "no-cache"
         },
-        body: chunks.map((chunk) => `data: ${JSON.stringify(chunk)}\n\n`).join("")
+        body: responsesFixture(chunks)
       });
     });
     await page.goto("/", { waitUntil: "domcontentloaded" });