refactor: remove leftover redundancies after card_game migration

Post-migration audit found the card_game/klondike migration essentially
complete; these are the four small redundancies that remained:

- core: delete dead GameState::compute_time_bonus (zero callers; engine
  uses the klondike_adapter free fn directly)
- data: drop dead public re-exports load_latest_replay_from /
  save_latest_replay_to (no callers outside replay.rs); keep
  latest_replay_path (engine legacy migration still uses it)
- data+engine: lift win-XP scoring into a shared XpBreakdown so the
  win-summary modal breakdown and xp_for_win share one source of truth
  instead of duplicating the speed/no-undo constants
- engine: replace feedback_anim_plugin's private foundation_from_slot
  copy with the canonical klondike_adapter::foundation_from_slot

cargo test --workspace + clippy -D warnings green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

solitaire_engine/src/feedback_anim_plugin.rs

@@ -44,7 +44,8 @@ use std::hash::{Hash, Hasher};
 use bevy::prelude::*;
 use bevy::window::RequestRedraw;
 use solitaire_core::card::Card;
-use solitaire_core::{Foundation, KlondikePile};
+use solitaire_core::KlondikePile;
+use solitaire_core::klondike_adapter::foundation_from_slot;
 use solitaire_data::AnimSpeed;
 
 use crate::animation_plugin::CardAnim;
@@ -645,16 +646,6 @@ fn pile_cards(
     }
 }
 
-fn foundation_from_slot(slot: u8) -> Option<Foundation> {
-    match slot {
-        0 => Some(Foundation::Foundation1),
-        1 => Some(Foundation::Foundation2),
-        2 => Some(Foundation::Foundation3),
-        3 => Some(Foundation::Foundation4),
-        _ => None,
-    }
-}
-
 // ---------------------------------------------------------------------------
 // Unit tests (pure functions only — no Bevy world required)
 // ---------------------------------------------------------------------------