feat(FN-1049): add per-agent heartbeat configuration via runtimeConfig

- Define AgentHeartbeatConfig interface in core types (heartbeatIntervalMs, heartbeatTimeoutMs, maxConcurrentRuns)
- Update HeartbeatMonitor to resolve per-agent config from AgentStore with validated min/max clamping
- Wire AgentStore into HeartbeatMonitor via InProcessRuntime initialization
- Add heartbeat settings section to dashboard AgentDetailView ConfigTab
- Add PATCH /api/agents/:id endpoint accepting runtimeConfig updates
- Add comprehensive tests for per-agent heartbeat config resolution and validation
- Document per-agent heartbeat configuration in AGENTS.md

packages/dashboard/src/routes.ts

@@ -7004,14 +7004,14 @@ Output ONLY the prompt text (no markdown, no explanations).`;
    */
   router.patch("/agents/:id", async (req, res) => {
     try {
-      const { name, role, metadata } = req.body;
+      const { name, role, metadata, runtimeConfig } = req.body;
 
       const scopedStore = await getScopedStore(req);
       const { AgentStore } = await import("@fusion/core");
       const agentStore = new AgentStore({ rootDir: scopedStore.getFusionDir() });
       await agentStore.init();
 
-      const agent = await agentStore.updateAgent(req.params.id, { name, role, metadata });
+      const agent = await agentStore.updateAgent(req.params.id, { name, role, metadata, runtimeConfig });
       res.json(agent);
     } catch (err: any) {
       if (err.message?.includes("not found")) {