feat(engine): first-launch polish — em-dash zero stats and welcome line on profile

On first launch the Stats grid previously mixed "0" cells (Games
Played / Won / Lost) with "—" cells (Best Score / Win Rate / Avg
Time), reading as inconsistent. Now every cell renders an em-dash
when games_played == 0, and a "Play a game to start tracking stats."
caption sits above the grid using the existing TYPE_CAPTION /
TEXT_SECONDARY tokens. Once a game has been played the original
formatters resume.

The Profile screen gains a one-line welcome ("Welcome! Play games to
earn XP and unlock achievements.") that renders only when both
total_xp and the daily streak are zero, breaking up the wall of
zero-valued readouts that greeted users on first launch.

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

solitaire_engine/src/profile_plugin.rs

@@ -111,6 +111,27 @@ fn spawn_profile_screen(
     spawn_modal(commands, ProfileScreen, Z_MODAL_PANEL, |card| {
         spawn_modal_header(card, "Profile", font_res);
 
+        // First-launch welcome — only when the player has zero XP and
+        // zero daily streak, so the profile doesn't read as a wall of
+        // zeros to a brand-new player.
+        if let Some(p) = progress
+            && p.0.total_xp == 0
+            && p.0.daily_challenge_streak == 0
+        {
+            card.spawn((
+                Text::new("Welcome! Play games to earn XP and unlock achievements."),
+                font_section.clone(),
+                TextColor(ACCENT_PRIMARY),
+                Node {
+                    margin: UiRect {
+                        bottom: VAL_SPACE_2,
+                        ..default()
+                    },
+                    ..default()
+                },
+            ));
+        }
+
         // ── Sync section ────────────────────────────────────────────
         card.spawn((
             Text::new("Sync"),

solitaire_engine/src/stats_plugin.rs

@@ -30,8 +30,8 @@ use crate::ui_modal::{
 };
 use crate::ui_theme::{
     ACCENT_PRIMARY, BORDER_SUBTLE, RADIUS_SM, STATE_INFO, STATE_WARNING, TEXT_PRIMARY,
-    TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG, TYPE_HEADLINE, VAL_SPACE_2, VAL_SPACE_3, VAL_SPACE_4,
+    TEXT_SECONDARY, TYPE_BODY, TYPE_BODY_LG, TYPE_CAPTION, TYPE_HEADLINE, VAL_SPACE_2, VAL_SPACE_3,
-    Z_MODAL_PANEL,
+    VAL_SPACE_4, Z_MODAL_PANEL,
 };
 
 /// Bevy resource wrapping the current stats.
@@ -247,14 +247,19 @@ fn spawn_stats_screen(
     font_res: Option<&FontResource>,
 ) {
     // --- primary stat cells ---
-    let win_rate_str    = format_win_rate(stats);
+    // First-launch zero-state: when no games have been played yet, render
-    let played_str      = format_stat_value(stats.games_played);
+    // every top-level cell as an em-dash so the panel doesn't read as a
-    let won_str         = format_stat_value(stats.games_won);
+    // mix of "0" counters and "—" sentinels (which feels buggy).
-    let lost_str        = format_stat_value(stats.games_lost);
+    let is_first_launch = stats.games_played == 0;
-    let fastest_str     = format_fastest_win(stats.fastest_win_seconds);
+    let dash = "\u{2014}".to_string();
-    let avg_time_str    = format_avg_time(stats);
+    let win_rate_str    = if is_first_launch { dash.clone() } else { format_win_rate(stats) };
-    let best_score_str  = format_optional_u32(stats.best_single_score);
+    let played_str      = if is_first_launch { dash.clone() } else { format_stat_value(stats.games_played) };
-    let best_streak_str = format_stat_value(stats.win_streak_best);
+    let won_str         = if is_first_launch { dash.clone() } else { format_stat_value(stats.games_won) };
+    let lost_str        = if is_first_launch { dash.clone() } else { format_stat_value(stats.games_lost) };
+    let fastest_str     = if is_first_launch { dash.clone() } else { format_fastest_win(stats.fastest_win_seconds) };
+    let avg_time_str    = if is_first_launch { dash.clone() } else { format_avg_time(stats) };
+    let best_score_str  = if is_first_launch { dash.clone() } else { format_optional_u32(stats.best_single_score) };
+    let best_streak_str = if is_first_launch { dash.clone() } else { format_stat_value(stats.win_streak_best) };
 
     let font_handle = font_res.map(|f| f.0.clone()).unwrap_or_default();
     let font_section = TextFont {
@@ -271,6 +276,27 @@ fn spawn_stats_screen(
     spawn_modal(commands, StatsScreen, Z_MODAL_PANEL, |card| {
         spawn_modal_header(card, "Statistics", font_res);
 
+        // First-launch caption — sits above the grid as gentle nudge so
+        // the wall of em-dashes reads as "nothing to track yet" rather
+        // than as broken state.
+        if is_first_launch {
+            card.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()
+                },
+            ));
+        }
+
         // --- primary stat cells grid ---
         card.spawn(Node {
             flex_direction: FlexDirection::Row,