Persist settings per-computer; add Reset to Defaults in General tab

- New core/app_settings.py: load/save settings.json to platform config dir
  (Windows: %APPDATA%, Linux: ~/.config, macOS: ~/Library/Application Support)
- MainWindow loads saved settings on startup, saves on every Apply & Close
- Settings survive profile switches and app restarts independently of profiles
- Settings > General: Reset to Defaults button with QMessageBox confirmation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 53 insertions, 0 deletions

diff --git a/core/app_settings.py b/core/app_settings.py
new file mode 100644
index 0000000..e8bc7ae
--- /dev/null
+++ b/core/app_settings.py
@@ -0,0 +1,53 @@
+"""
+core/app_settings.py
+
+Platform-aware persistence for application settings.
+
+Stored independently of profiles so they survive profile switches and
+reflect per-computer preferences (theme, font, paths, etc.).
+
+Locations:
+  Windows : %APPDATA%/labUI/settings.json
+  macOS   : ~/Library/Application Support/labUI/settings.json
+  Linux   : $XDG_CONFIG_HOME/labUI/settings.json  (default ~/.config/labUI/)
+"""
+
+import json
+import os
+import sys
+from pathlib import Path
+
+
+def _settings_path() -> Path:
+    if sys.platform == "win32":
+        base = Path(os.environ.get("APPDATA", Path.home()))
+    elif sys.platform == "darwin":
+        base = Path.home() / "Library" / "Application Support"
+    else:
+        base = Path(os.environ.get("XDG_CONFIG_HOME", Path.home() / ".config"))
+    return base / "labUI" / "settings.json"
+
+
+SETTINGS_PATH = _settings_path()
+
+
+def load_settings(defaults: dict) -> dict:
+    """Return defaults merged with any saved settings. Never raises."""
+    cfg = dict(defaults)
+    try:
+        if SETTINGS_PATH.exists():
+            with open(SETTINGS_PATH) as f:
+                cfg.update(json.load(f))
+    except Exception:
+        pass
+    return cfg
+
+
+def save_settings(cfg: dict) -> None:
+    """Persist cfg to disk. Never raises."""
+    try:
+        SETTINGS_PATH.parent.mkdir(parents=True, exist_ok=True)
+        with open(SETTINGS_PATH, "w") as f:
+            json.dump(cfg, f, indent=2)
+    except Exception:
+        pass