feat(desktop): 标题画面两秒确定性入场动画

entranceProgress 纯函数按帧计数（固定 60Hz 步长，禁实时时钟）：黛瓦天际线自上 36px 落定、标题自下 24px 升起、水面带 2s 淡入、灯笼/面板同步；快照回归断言进度锚点（0/60/120/超时）与确定性；LV_AUTOPLAY_FLOW 标题停留 60 帧可直接采样入场过程。

1 files changed, 11 insertions, 7 deletions

diff --git a/src/LivingVillage.Desktop/Game.fs b/src/LivingVillage.Desktop/Game.fs
index 9464c8b..51fa74d 100644
--- a/src/LivingVillage.Desktop/Game.fs
+++ b/src/LivingVillage.Desktop/Game.fs
@@ -595,19 +595,22 @@ type LivingVillageGame() as this =
             let y1 = if index = bandCount - 1 then height else y0 + bandHeight
             spriteBatch.Draw(pixel, Rectangle(0, y0, width, y1 - y0), Color(band.R, band.G, band.B))) layout.SkyBands
 
-        // Jiangnan skyline: eave tiles continuously, ridge tiles rising above them.
+        // Deterministic 2s entrance: skyline settles from above as the progress unwinds.
+        let entrance = TitleScreen.entranceProgress hudClock
+        let skylineDrop = int (36.0f * entrance)
         List.iteri (fun column slot ->
             let x = column * Sim.tilePixels
             let source = VillageArt.atlasTileRectangle slot
             if slot = fst TitleScreen.roofSlots then
-                spriteBatch.Draw(artTextures.TileAtlas, Rectangle(x, layout.RidgeY, Sim.tilePixels, Sim.tilePixels), source, Color.White)
-            spriteBatch.Draw(artTextures.TileAtlas, Rectangle(x, layout.EaveY, Sim.tilePixels, Sim.tilePixels), VillageArt.atlasTileRectangle (snd TitleScreen.roofSlots), Color.White))
+                spriteBatch.Draw(artTextures.TileAtlas, Rectangle(x, layout.RidgeY + skylineDrop, Sim.tilePixels, Sim.tilePixels), source, Color.White)
+            spriteBatch.Draw(artTextures.TileAtlas, Rectangle(x, layout.EaveY + skylineDrop, Sim.tilePixels, Sim.tilePixels), VillageArt.atlasTileRectangle (snd TitleScreen.roofSlots), Color.White))
             layout.RoofTileSlots
 
         // Water band drawn from the atlas water tile, reflecting the skyline above.
+        let waterColor = Color(150, 170, 178, int (255.0f * (1.0f - entrance)))
         for row in layout.WaterRows do
             for x in 0 .. Sim.tilePixels .. width - 1 do
-                spriteBatch.Draw(artTextures.TileAtlas, Rectangle(x, row, Sim.tilePixels, Sim.tilePixels), VillageArt.atlasTileRectangle TitleScreen.waterSlot, Color(150, 170, 178))
+                spriteBatch.Draw(artTextures.TileAtlas, Rectangle(x, row, Sim.tilePixels, Sim.tilePixels), VillageArt.atlasTileRectangle TitleScreen.waterSlot, waterColor)
 
         // Lantern glows along the water bank.
         let lanternColor, lanternHalo = TitleScreen.lanternColors
@@ -617,9 +620,10 @@ type LivingVillageGame() as this =
             spriteBatch.Draw(pixel, Rectangle(lx - 1, ly - 7, 4, 2), Color(90, 60, 40))
             spriteBatch.Draw(pixel, Rectangle(lx - 2, ly + 5, 6, 2), Color(90, 60, 40))
 
-        // Title: large CJK atlas glyphs with a soft shadow for readability.
-        PixelText.draw spriteBatch pixel cjkAtlas (layout.TitleX + 4) (layout.TitleY + 4) layout.TitleScale (Color(12, 20, 28)) layout.TitleText
-        PixelText.draw spriteBatch pixel cjkAtlas layout.TitleX layout.TitleY layout.TitleScale (Color(235, 246, 232)) layout.TitleText
+        // Title rises into place as the entrance progress unwinds.
+        let titleLift = int (24.0f * entrance)
+        PixelText.draw spriteBatch pixel cjkAtlas (layout.TitleX + 4) (layout.TitleY + titleLift + 4) layout.TitleScale (Color(12, 20, 28)) layout.TitleText
+        PixelText.draw spriteBatch pixel cjkAtlas layout.TitleX (layout.TitleY + titleLift) layout.TitleScale (Color(235, 246, 232)) layout.TitleText
 
         // Menu panel floats over the lower half; translucent so the scene layers stay visible.
         spriteBatch.Draw(pixel, Rectangle(panelX, panelY, panelWidth, panelHeight), Color(11, 19, 27, 200))