Flag guests that no backup job covers

The guest table marks with "!" each guest that Proxmox's not-backed-up
list returns. The frame's bottom border shows the count, e.g.
"mainframe · 2 without backup job". This uses Proxmox's own answer, so
it also counts jobs that select guests by pool.

If the coverage call fails, the guests are still listed and a warning
says the coverage is unknown.

Closes #9

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_app.py

@@ -49,6 +49,7 @@ class Fake:
         self.use_error = None
         self.use_hook = None
         self.guests_by_context = {}
+        self.unprotected, self.unprotected_error = set(), None
         self.list_hook = None
         # delivery A (guest info screen)
         self.net_configs = {}  # vmid -> extra config keys (netN, ipconfigN)
@@ -103,6 +104,11 @@ class Fake:
         self.status_calls.append(guest["vmid"])
         return self.live_status.get(guest["vmid"], guest["status"])
 
+    def not_backed_up(self):
+        if self.unprotected_error:
+            raise self.unprotected_error
+        return set(self.unprotected)
+
     def contexts(self):
         self.contexts_calls += 1
         if self.contexts_error:
@@ -195,6 +201,7 @@ def fake(monkeypatch):
         "backup_now",
         "bridges",
         "set_net",
+        "not_backed_up",
     ):
         monkeypatch.setattr(cli, name, getattr(f, name), raising=False)
     for name in ("list_guests", "guest_config", "disks", "action", "set_resources",
@@ -2108,3 +2115,39 @@ async def test_info_resources_reload_after_edit(fake, monkeypatch):
         await settle(app, pilot)
         assert isinstance(app.screen, appmod.InfoScreen)
         assert resource_rows(app)["CPU"].startswith("8 cores")
+
+
+# --- #9: flag guests that no backup job covers --------------------------------------
+
+
+def first_cell(app, vmid):
+    return str(app.query_one("#guests", DataTable).get_row(str(vmid))[0])
+
+
+async def test_unprotected_guests_are_marked_and_counted(fake):
+    fake.unprotected = {100}
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await settle(app, pilot)
+        assert first_cell(app, 100) == "!"
+        assert first_cell(app, 108) == ""
+        subtitle = str(app.query_one("#guests_section").border_subtitle)
+        assert "mainframe" in subtitle and "1 without backup job" in subtitle
+
+
+async def test_no_count_when_every_guest_is_covered(fake):
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await settle(app, pilot)
+        assert str(app.query_one("#guests_section").border_subtitle) == "mainframe"
+        assert first_cell(app, 100) == "" and first_cell(app, 108) == ""
+
+
+async def test_backup_coverage_failure_still_lists_guests(fake):
+    fake.unprotected_error = cli.CliError("Error: boom")
+    app = make_app()
+    async with app.run_test(size=SIZE) as pilot:
+        await settle(app, pilot)
+        assert app.query_one("#guests", DataTable).row_count == 2
+        assert any(sev == "warning" for _, sev in app.seen)  # coverage unknown, said so
+        assert app.is_running