fix(engine): resolve input coordination bugs in selection/pause/keyboard

- SelectionPlugin: add clear_selection_on_state_change system so undo/move/reject
  never leave a stale selection pointing at the wrong card
- SelectionPlugin: expose SelectionKeySet system set for cross-plugin ordering
- PausePlugin: skip Escape→pause when a card is keyboard-selected; toggle_pause
  now runs before SelectionKeySet so it reads SelectionState before it is cleared
- InputPlugin: guard Space→DrawRequestEvent when SelectionState has an active pile
  so Space executes a card move instead of also drawing from stock
- window: enforce 800×600 minimum via WindowResizeConstraints
- game_state: add precondition doc to next_auto_complete_move (waste exclusion)
- card_plugin: 12 unit tests for constants, face_colour, label_visibility, label_for
- pause_plugin: add paused_resource_default and draw_mode_label exhaustiveness tests

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

solitaire_app/src/main.rs

@@ -22,6 +22,11 @@ fn main() {
                 primary_window: Some(Window {
                     title: "Solitaire Quest".into(),
                     resolution: (1280u32, 800u32).into(),
+                    resize_constraints: bevy::window::WindowResizeConstraints {
+                        min_width: 800.0,
+                        min_height: 600.0,
+                        ..default()
+                    },
                     ..default()
                 }),
                 ..default()