feat(settings): "Smart window size" toggle to opt out of monitor-relative

launch sizing

Players who specifically prefer the literal 1280×800 baseline on
every fresh-install launch had no way to opt out of the v0.19.0
smart-default sizer. Adds a Gameplay-section toggle (mirrors the
"Winnable deals only" pattern) so they can flip it off.

- New `Settings::disable_smart_default_size: bool` field with
  `#[serde(default)]` so legacy `settings.json` files load to the
  shipped behaviour (smart sizer enabled).
- Settings panel gains a "Smart window size" row with ON/OFF label
  inverting the negative flag, and a tooltip clarifying that saved
  window geometry always wins over both branches.
- `solitaire_app::main` reads the flag once at startup and skips
  the `apply_smart_default_window_size` registration when it's set.
  Mid-session changes apply on next launch (documented on the
  field).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

solitaire_app/src/main.rs

@@ -153,7 +153,12 @@ fn main() {
     // monitor opens the same 1280×800 window that a 1080p monitor
     // does — visually tiny relative to screen. Skipped entirely when
     // saved geometry was applied; the player's preference always wins.
-    if !had_saved_geometry {
+    //
+    // Players who specifically want the literal 1280×800 baseline on
+    // every fresh launch can flip `disable_smart_default_size` in
+    // Settings to opt out. The flag is checked once at startup; a
+    // mid-session change applies on the next launch.
+    if !had_saved_geometry && !settings.disable_smart_default_size {
         app.add_systems(Update, apply_smart_default_window_size);
     }