fix(manage): render container warning with real line breaks

manage.sh

@@ -1550,7 +1550,7 @@ UPGRADEEOF
         fi
         echo "✓ Configuration preserved"
         if [[ -n "$container_note" ]]; then
-            echo "$container_note"
+            printf '%b\n' "$container_note"
         fi
     else
         show_info "Upgrade Complete" "Upgrade completed successfully!\n\nVersion: $current_version → $new_version\n\n✓ Configuration preserved${container_note}"

tests/test_manage_upgrade_output.py

@@ -0,0 +1,46 @@
+"""Exercise the upgrade summary without running installation/service commands."""
+
+import os
+import subprocess
+from pathlib import Path
+
+import pytest
+
+
+@pytest.mark.parametrize("service_running", [0, 1])
+def test_silent_upgrade_container_warning_renders_newlines(service_running):
+    script = (Path(__file__).resolve().parents[1] / "manage.sh").read_text()
+    start = script.index('    local container_note=""')
+    end = script.index("\n    return 0\n}", start)
+    summary = script[start:end]
+    # The nonempty container variable selects the warning without depending on
+    # the test host. Only the final output block runs, not manage.sh itself.
+    probe = (
+        "set -eu\nrender() {\n"
+        "local silent=true container=test current_version=old new_version=new\n"
+        f"local service_was_running={service_running} service_was_enabled=0\n"
+        f"{summary}\n}}\nrender\n"
+    )
+    env = os.environ.copy()
+    env.pop("BASH_ENV", None)
+    result = subprocess.run(
+        ["bash", "--noprofile", "--norc"],
+        input=probe,
+        text=True,
+        capture_output=True,
+        check=True,
+        env=env,
+    )
+    expected = "Upgrade completed successfully!\nVersion: old -> new\n"
+    if service_running:
+        expected += "✓ Service is running\n"
+    expected += (
+        "✓ Configuration preserved\n\n\n"
+        "⚠ CONTAINER DETECTED:\n"
+        "USB udev rules must be set on the HOST, not here.\n"
+        "CH341 host-side setup: "
+        "https://docs.openhop.dev/projects/openhop-repeater/hardware-setup/#ch341-usb-spi-hosts\n"
+        "=== Upgrade Complete ===\n"
+    )
+    assert result.stdout == expected
+    assert result.stderr == ""