fix: stabilize tailscale enrollment without cloud-init rollback

Create /etc/tailscale before writing runtime key, add progress logging and unbuffered output in enroll script, and shorten guest-agent wait to fail faster when enrollment cannot run.

.gitea/workflows/terraform-apply.yml

@@ -144,15 +144,21 @@ jobs:
                   payload = resp.read().decode("utf-8")
               return json.loads(payload)
 
-          def wait_for_guest_agent(vmid, timeout_seconds=900):
+          def wait_for_guest_agent(vmid, timeout_seconds=300):
               deadline = time.time() + timeout_seconds
+              tries = 0
               while time.time() < deadline:
+                  tries += 1
                   try:
                       res = api_request("GET", f"/api2/json/nodes/{target_node}/qemu/{vmid}/agent/ping")
                       if res.get("data") == "pong":
+                          print(f"Guest agent ready for vmid {vmid}", flush=True)
                           return True
                   except Exception:
                       pass
+                  if tries % 6 == 0:
+                      remaining = int(deadline - time.time())
+                      print(f"Waiting for guest agent on vmid {vmid} ({remaining}s left)", flush=True)
                   time.sleep(5)
               return False
 
@@ -193,6 +199,7 @@ jobs:
               safe_hostname = hostname.replace("'", "'\"'\"'")
               cmd = (
                   "set -e; "
+                  "install -d -m 700 /etc/tailscale; "
                   f"printf '%s' '{safe_key}' > /etc/tailscale/authkey; "
                   f"printf '%s' '{safe_hostname}' > /etc/tailscale/hostname; "
                   "chmod 600 /etc/tailscale/authkey; "
@@ -227,4 +234,4 @@ jobs:
           print("\nTailscale enrollment completed for all managed VMs")
           PY
 
-          python3 enroll_tailscale.py
+          python3 -u enroll_tailscale.py