fix(engine-b): Proxmox agent exec repeated command fields; Traefik write throws on failure

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/Services/Proxmox/HttpProxmoxClient.php

@@ -96,11 +96,16 @@ class HttpProxmoxClient implements ProxmoxClient
 
     public function guestExec(string $node, int $vmid, string $command): array
     {
-        // The guest agent runs a program directly, not a shell — wrap compound
-        // commands (cd/&&/pipes/redirects/env) in an explicit shell. Proxmox is
-        // form-encoded and takes `command` as an argv list.
-        $pid = $this->http()->asForm()
-            ->post("/nodes/{$node}/qemu/{$vmid}/agent/exec", ['command' => ['/bin/sh', '-c', $command]])
+        // Wrap compound commands (cd/&&/pipes/redirects/env) in an explicit shell
+        // — the agent execs a program directly. Proxmox wants the argv as REPEATED
+        // `command=` fields (not indexed command[0]=…), so build the body by hand.
+        $body = collect(['/bin/sh', '-c', $command])
+            ->map(fn ($arg) => 'command='.rawurlencode($arg))
+            ->implode('&');
+
+        $pid = $this->http()
+            ->withBody($body, 'application/x-www-form-urlencoded')
+            ->post("/nodes/{$node}/qemu/{$vmid}/agent/exec")
             ->throw()->json('data.pid');
 
         // Poll exec-status until the command has exited.

app/Services/Traefik/SshTraefikWriter.php

@@ -3,6 +3,7 @@
 namespace App\Services\Traefik;
 
 use Illuminate\Support\Facades\Http;
+use RuntimeException;
 
 /**
  * Writes Traefik file-provider YAML into the configured dynamic directory (where
@@ -19,7 +20,9 @@ class SshTraefikWriter implements TraefikWriter
         $yaml = $this->render($subdomain, $fqdn, $targetHost);
 
         $path = rtrim((string) config('provisioning.traefik.dynamic_path'), '/')."/{$subdomain}.yml";
-        file_put_contents($path, $yaml);
+        if (file_put_contents($path, $yaml) === false) {
+            throw new RuntimeException("Failed to write Traefik config: {$path}");
+        }
     }
 
     public function remove(string $subdomain): void