polish(engine): standard empty/loading/error states (Phase L)

New ui_modal::spawn_empty_state — glyph + headline + optional detail,
centred, with next-step actions composed alongside rather than
configured in. Glyphs restricted to FiraMono-covered ranges (suits,
arrows, ASCII) per the section-10/11 Android constraint.

Swept every improvised surface onto it:
- Theme store: loading / error / empty-catalog branches
- Leaderboard: fetching / error / be-the-first branches
- You-hub Replays tab: dedicated no-replays state (selector and
  actions no longer spawn dead controls when history is empty)
- Stats: first-launch nudge above the em-dash grid

The Account tab's sync row was deliberately NOT swept: it is a live
status + action row, not an empty state, and its deeper treatment
belongs to Phase M's sync-transparency work.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

solitaire_engine/src/stats_plugin.rs

@@ -30,7 +30,7 @@ use crate::ui_modal::{ButtonVariant, ModalButton, spawn_modal_button};
 use crate::ui_theme::{
     ACCENT_PRIMARY, BG_ELEVATED_HI, BORDER_SUBTLE, HighContrastBorder, RADIUS_SM, STATE_INFO,
     STATE_WARNING, STREAK_MILESTONES, TEXT_PRIMARY, TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG,
-    TYPE_CAPTION, TYPE_HEADLINE, VAL_SPACE_1, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4,
+    TYPE_HEADLINE, VAL_SPACE_1, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4,
 };
 
 /// Bevy resource wrapping the current stats.
@@ -719,25 +719,17 @@ pub(crate) fn spawn_stats_body(
             },
         ))
         .with_children(|body| {
-            // First-launch caption — sits above the grid as gentle nudge so
+            // First-launch empty state (Phase L) — sits above the grid so
             // the wall of em-dashes reads as "nothing to track yet" rather
             // than as broken state.
             if is_first_launch {
-                body.spawn((
-                    Text::new("Play a game to start tracking stats."),
-                    TextFont {
-                        font_size: TYPE_CAPTION,
-                        ..default()
-                    },
-                    TextColor(TEXT_SECONDARY),
-                    Node {
-                        margin: UiRect {
-                            bottom: VAL_SPACE_2,
-                            ..default()
-                        },
-                        ..default()
-                    },
-                ));
+                crate::ui_modal::spawn_empty_state(
+                    body,
+                    "\u{2663}",
+                    "Play a game to start tracking stats.",
+                    None,
+                    font_res,
+                );
             }
 
             // --- primary stat cells grid ---
@@ -893,6 +885,20 @@ pub(crate) fn spawn_replays_body(
     selected_index: usize,
     font_res: Option<&FontResource>,
 ) {
+    // Standard empty state (Phase L) — the selector / Watch / Copy
+    // controls only spawn when there is something to select, so their
+    // handlers all no-op via their existing empty-query paths.
+    if replays.is_empty() {
+        crate::ui_modal::spawn_empty_state(
+            card,
+            "\u{2666}",
+            "No replays yet.",
+            Some("Every win records a replay here automatically."),
+            font_res,
+        );
+        return;
+    }
+
     let font_handle = font_res.map(|f| f.0.clone()).unwrap_or_default();
     let font_row = TextFont {
         font: font_handle,