feat(cli): add --title flag to set tab title when summoning

Add a --title <title> flag to the dispatch CLI so a summoned agent's
conversation/tab gets a human-readable title at creation time instead of the
auto-derived default (Untitled until the first message append).

The title is carried as an additive optional ChatRequest.title field (the
HTTP client-server contract), parsed + trimmed server-side in parseChatBody,
and persisted via the conversation store's setConversationTitle in the POST
/chat route BEFORE the turn starts — so the title is set atomically with
creation and before --open signals the frontend to open the tab. No second
HTTP round-trip is needed.

A whitespace-only title is treated as absent (auto-derive); a non-string
title yields HTTP 400. A title-set failure is logged but never blocks the
turn (the title is a nicety, the answer is not). The change is purely
additive — no existing behavior or assertion changes.

Verification: typecheck EXIT 0; test 2021 passed | 6 skipped | 0 failed;
check EXIT 0 (12 pre-existing warnings in untouched files).

1 files changed, 39 insertions, 0 deletions

diff --git a/packages/cli/src/message.test.ts b/packages/cli/src/message.test.ts
index 536d64f..2deb197 100644
--- a/packages/cli/src/message.test.ts
+++ b/packages/cli/src/message.test.ts
@@ -111,6 +111,22 @@ describe("buildChatRequest", () => {
     );
     expect(req).not.toHaveProperty("workspaceId");
   });
+
+  it("includes title when provided", () => {
+    const req = buildChatRequest(
+      { modelName: "m", text: "x", title: "My Task", showReasoning: false },
+      { cwd: "/work", message: "x" },
+    );
+    expect(req.title).toBe("My Task");
+  });
+
+  it("omits title when not provided", () => {
+    const req = buildChatRequest(
+      { modelName: "m", text: "x", showReasoning: false },
+      { cwd: "/work", message: "x" },
+    );
+    expect(req).not.toHaveProperty("title");
+  });
 });
 
 describe("workspace flag → ChatRequest", () => {
@@ -145,3 +161,26 @@ describe("workspace flag → ChatRequest", () => {
     expect(req.workspaceId).toBe("shorthand");
   });
 });
+
+describe("title flag → ChatRequest", () => {
+  const defaultServer = "http://localhost:24203";
+
+  it("--title flag sets title on request", () => {
+    const parsed = parseArgs(["my-model", "--text", "hi", "--title", "My Task"], {
+      defaultServer,
+    });
+    expect(parsed.kind).toBe("chat");
+    if (parsed.kind !== "chat") return;
+    const req = buildChatRequest(parsed, { cwd: "/work", message: "hi" });
+    expect(req.title).toBe("My Task");
+  });
+
+  it("--title flag omitted sends no title", () => {
+    const parsed = parseArgs(["my-model", "--text", "hi"], { defaultServer });
+    expect(parsed.kind).toBe("chat");
+    if (parsed.kind !== "chat") return;
+    const req = buildChatRequest(parsed, { cwd: "/work", message: "hi" });
+    expect(req.title).toBeUndefined();
+    expect(req).not.toHaveProperty("title");
+  });
+});