feat(FN-2920): improve remote tunnel setup and heartbeat scheduling

- Add cloudflared install/detection support in remote settings API, UI, and route tests
- Surface Cloudflare tunnel prerequisites in Settings modal with remote access docs updates
- Harden heartbeat runtime scheduling by avoiding stale timeout state and simplifying runtime timeout handling
- Expand CLI/core/dashboard/engine coverage for task lifecycle, agent health, and runtime heartbeat behavior
- Add changesets for heartbeat scheduling fixes and PR approval setting updates

Fusion-Task-Id: FN-2920

packages/dashboard/app/api/legacy.ts

@@ -462,6 +462,7 @@ export interface RemoteStatus {
   url: string | null;
   lastError: string | null;
   lastErrorCode?: string | null;
+  cloudflaredAvailable?: boolean | null;
   restore?: {
     outcome: "applied" | "skipped" | "failed";
     reason: string;
@@ -489,6 +490,12 @@ export function fetchRemoteStatus(projectId?: string): Promise<RemoteStatus> {
   return api<RemoteStatus>(withProjectId("/remote/status", projectId));
 }
 
+export function installCloudflared(projectId?: string): Promise<{ success: boolean; command: string; error?: string }> {
+  return api(withProjectId("/remote/install-cloudflared", projectId), {
+    method: "POST",
+  });
+}
+
 export function activateRemoteProvider(provider: "tailscale" | "cloudflare", projectId?: string): Promise<{ activeProvider: "tailscale" | "cloudflare" }> {
   return api<{ activeProvider: "tailscale" | "cloudflare" }>(withProjectId("/remote/provider/activate", projectId), {
     method: "POST",