Add comprehensive test suite achieving 99% code coverage

Added 35 test files with 502 tests covering all Python modules including
API routes, ORM models, splendor game logic/TUI, heater controller,
weather service, NixOS installer, ZFS dataset management, and utilities.
Coverage improved from 11% to 99% (2540/2564 statements covered).

https://claude.ai/code/session_01SVzgLDUS1Cdc4eh1ijETTh

tests/test_installer_main_extended.py

@@ -0,0 +1,50 @@
+"""Extended tests for python/installer/__main__.py."""
+
+from __future__ import annotations
+
+import sys
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from python.installer.__main__ import (
+    create_zfs_datasets,
+    create_zfs_pool,
+    get_boot_drive_id,
+    partition_disk,
+)
+
+
+def test_create_zfs_datasets() -> None:
+    """Test create_zfs_datasets creates expected datasets."""
+    with patch("python.installer.__main__.bash_wrapper") as mock_bash:
+        mock_bash.return_value = "NAME\nroot_pool\nroot_pool/root\nroot_pool/home\nroot_pool/var\nroot_pool/nix\n"
+        create_zfs_datasets()
+    assert mock_bash.call_count == 5  # 4 create + 1 list
+
+
+def test_create_zfs_datasets_missing(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Test create_zfs_datasets exits on missing datasets."""
+    with (
+        patch("python.installer.__main__.bash_wrapper") as mock_bash,
+        pytest.raises(SystemExit),
+    ):
+        mock_bash.return_value = "NAME\nroot_pool\n"
+        create_zfs_datasets()
+
+
+def test_create_zfs_pool_failure(monkeypatch: pytest.MonkeyPatch) -> None:
+    """Test create_zfs_pool exits on failure."""
+    with (
+        patch("python.installer.__main__.bash_wrapper") as mock_bash,
+        pytest.raises(SystemExit),
+    ):
+        mock_bash.return_value = "NAME\n"
+        create_zfs_pool(["/dev/sda-part2"], "/mnt")
+
+
+def test_get_boot_drive_id() -> None:
+    """Test get_boot_drive_id extracts UUID."""
+    with patch("python.installer.__main__.bash_wrapper", return_value="UUID\nABCD-1234\n"):
+        result = get_boot_drive_id("/dev/sda")
+    assert result == "ABCD-1234"