feat(FN-3864): add mesh lease recovery and compact assigned-agent badge

- Add mesh lease manager integration so engine/self-healing can recover and reconcile stale lease state
- Extend core store/agent-store types, DB handling, and tests to track lease recovery semantics across runtimes
- Collapse TaskCard assigned-agent badge label in narrow cards while preserving accessible labeling behavior
- Update dashboard and engine test coverage for lease recovery flows and assigned-agent badge accessibility
- Document mesh lease recovery behavior in architecture, multi-project, and agents docs

Fusion-Task-Id: FN-3864

packages/dashboard/app/components/TaskCard.css

@@ -12,6 +12,8 @@
     opacity var(--transition-normal);
   user-select: none;
   touch-action: pan-x pan-y;
+  container-type: inline-size;
+  container-name: task-card;
 }
 .card:hover {
   background: var(--card-hover);
@@ -475,13 +477,13 @@
 .card-agent-badge {
   display: inline-flex;
   align-items: center;
-  gap: 4px;
+  gap: var(--space-xs);
   font-size: 0.625rem;
   font-weight: 600;
   color: var(--text-muted);
   background: color-mix(in srgb, var(--text-muted) 18%, transparent);
-  border: 1px solid color-mix(in srgb, var(--text-muted) 35%, transparent);
-  padding: 2px 6px;
+  border: var(--btn-border-width) solid color-mix(in srgb, var(--text-muted) 35%, transparent);
+  padding: calc(var(--space-xs) / 4) calc(var(--space-sm) - (var(--space-xs) / 4));
   border-radius: var(--radius-pill);
   overflow: hidden;
   text-overflow: ellipsis;
@@ -504,11 +506,24 @@
 
 .card-agent-badge-text {
   min-width: 0;
+  flex: 0 1 auto;
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
 }
 
+@container task-card (max-width: 240px) {
+  .card-agent-badge-text {
+    display: none;
+  }
+}
+
+@media (max-width: 768px) {
+  .card-agent-badge-text {
+    display: none;
+  }
+}
+
 .card-agent-badge--loading {
   animation: pulse 1.5s ease-in-out infinite;
 }

packages/dashboard/app/components/TaskCard.tsx

@@ -1663,9 +1663,10 @@ function TaskCardComponent({
               title={`Assigned to ${agentName ?? task.assignedAgentId}`}
             >
               <Bot size={11} />
-              <span className="card-agent-badge-text">
+              <span className="card-agent-badge-text" aria-hidden="true">
                 {abbreviateBadge(agentName ?? task.assignedAgentId, 15)}
               </span>
+              <span className="visually-hidden">Assigned to {agentName ?? task.assignedAgentId}</span>
             </span>
           )}
         </div>

packages/dashboard/app/components/__tests__/TaskCard.test.tsx

@@ -1371,6 +1371,35 @@ describe("TaskCard provider icons on agent row", () => {
     expect(screen.getByTestId("provider-icon-anthropic")).toBeDefined();
   });
 
+  it("keeps assigned agent badge accessible when label is visually collapsible", async () => {
+    vi.mocked(fetchAgent).mockResolvedValue({
+      id: "agent-robot",
+      name: "Task Robot",
+      role: "executor",
+      state: "active",
+      metadata: {},
+      heartbeatHistory: [],
+      completedRuns: [],
+      createdAt: "2026-01-01T00:00:00.000Z",
+      updatedAt: "2026-01-01T00:00:00.000Z",
+    } as any);
+
+    const { container } = render(
+      <TaskCard
+        task={makeTask({ modelProvider: "anthropic", assignedAgentId: "agent-robot" })}
+        onOpenDetail={noop}
+        addToast={noop}
+      />,
+    );
+
+    await waitFor(() => {
+      const badge = container.querySelector(".card-agent-badge");
+      expect(badge).not.toBeNull();
+      expect(badge?.getAttribute("title")).toBe("Assigned to Task Robot");
+      expect(badge?.querySelector(".visually-hidden")?.textContent).toContain("Assigned to Task Robot");
+    });
+  });
+
   it("deduplicates when executor and validator use same provider", () => {
     render(
       <TaskCard
@@ -1676,8 +1705,9 @@ describe("TaskCard agent badge", () => {
     );
 
     await waitFor(() => {
-      expect(screen.getByTitle("Assigned to Task Robot")).toBeDefined();
-      expect(screen.getByText("Task Robot")).toBeDefined();
+      const badge = screen.getByTitle("Assigned to Task Robot");
+      expect(badge).toBeDefined();
+      expect(badge.querySelector(".visually-hidden")?.textContent).toContain("Assigned to Task Robot");
     });
   });