fix: canonicalize workspace tab routes and prevent orphan runs

packages/app/src/screens/workspace/workspace-tab-model.test.ts

@@ -114,7 +114,7 @@ describe("deriveWorkspaceTabModel", () => {
     ]);
   });
 
-  it("prefers route tab, then focused tab, then first tab for active selection", () => {
+  it("prefers route tab when present, then focused tab, then first tab for active selection", () => {
     const base = {
       workspaceAgents: [makeAgent({ id: "agent-a" }), makeAgent({ id: "agent-b" })],
       terminals: [],
@@ -136,6 +136,54 @@ describe("deriveWorkspaceTabModel", () => {
         routeTabId: "agent_agent-a",
       }).activeTabId
     ).toBe("agent_agent-a");
+
+    expect(
+      deriveWorkspaceTabModel({
+        ...base,
+        focusedTabId: "agent_agent-b",
+        routeTabId: "agent_agent-missing",
+      }).activeTabId
+    ).toBe("agent_agent-b");
+  });
+
+  it("switches active tab target when route tab id changes", () => {
+    const modelA = deriveWorkspaceTabModel({
+      workspaceAgents: [makeAgent({ id: "agent-a" }), makeAgent({ id: "agent-b" })],
+      terminals: [{ id: "term-1", name: "shell" }],
+      uiTabs: [],
+      tabOrder: ["agent_agent-a", "terminal_term-1", "agent_agent-b"],
+      routeTabId: "terminal_term-1",
+    });
+
+    const modelB = deriveWorkspaceTabModel({
+      workspaceAgents: [makeAgent({ id: "agent-a" }), makeAgent({ id: "agent-b" })],
+      terminals: [{ id: "term-1", name: "shell" }],
+      uiTabs: [],
+      tabOrder: ["agent_agent-a", "terminal_term-1", "agent_agent-b"],
+      routeTabId: "agent_agent-b",
+    });
+
+    expect(modelA.activeTab?.descriptor.tabId).toBe("terminal_term-1");
+    expect(modelA.activeTab?.target.kind).toBe("terminal");
+    expect(modelB.activeTab?.descriptor.tabId).toBe("agent_agent-b");
+    expect(modelB.activeTab?.target.kind).toBe("agent");
+  });
+
+  it("re-resolves active content for a new workspace when prior focused tab is not available", () => {
+    const model = deriveWorkspaceTabModel({
+      workspaceAgents: [makeAgent({ id: "workspace-b-agent", title: "B" })],
+      terminals: [],
+      uiTabs: [],
+      tabOrder: ["agent_workspace-b-agent"],
+      focusedTabId: "agent_workspace-a-agent",
+      routeTabId: null,
+    });
+
+    expect(model.activeTabId).toBe("agent_workspace-b-agent");
+    expect(model.activeTab?.target).toEqual({
+      kind: "agent",
+      agentId: "workspace-b-agent",
+    });
   });
 
   it("covers regression: non-archived attention agent remains visible even if UI tabs omitted it", () => {