song select: refresh a folder's song count text when the count changes

The folder texts are cached on first draw, but the engine fills in a
folder's song count with a background scan after the boxes are first
drawn, so the count text stayed at 0 for the rest of the session (e.g.
the folder under the cursor at startup kept showing 0 songs). The cache
now remembers the count it was built with and rebuilds that one text
when box.tja_count changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitattributes

@@ -1 +1,5 @@
 * -text
+*.png filter=lfs diff=lfs merge=lfs -text
+*.ogg filter=lfs diff=lfs merge=lfs -text
+*.mp4 filter=lfs diff=lfs merge=lfs -text
+*.wav filter=lfs diff=lfs merge=lfs -text

Graphics/background/animation.json

@@ -36,22 +36,13 @@
     {
         "id": 4,
         "type": "move",
-        "duration": 266,
-        "total_distance": -40,
-        "ease_out": "quadratic",
-        "comment": "donbg 3,5 bounce up"
-    },
-    {
-        "id": 5,
-        "type": "move",
-        "duration": 266,
-        "total_distance": -40,
+        "duration": 532,
+        "total_distance": 0,
         "ease_in": "quadratic",
-        "delay": {
-            "reference_id": 4,
-            "property": "duration"
-        },
-        "comment": "donbg 3,5 bounce down"
+        "waypoints": [
+            { "at": 266, "value": -40, "ease_out": "quadratic" }
+        ],
+        "comment": "donbg 3,5 bounce up/down (merged from old ids 4+5)"
     },
     {
         "id": 6,
@@ -62,11 +53,7 @@
         "ease_in": "quadratic",
         "ease_out": "quadratic",
         "delay": {
-            "init_val": {
-                "reference_id": 4,
-                "property": "duration"
-            },
-            "reference_id": 5,
+            "reference_id": 4,
             "property": "duration"
         },
         "loop": true,
@@ -82,11 +69,7 @@
         "ease_out": "quadratic",
         "delay": {
             "init_val": {
-                "init_val": {
-                    "reference_id": 4,
-                    "property": "duration"
-                },
-                "reference_id": 5,
+                "reference_id": 4,
                 "property": "duration"
             },
             "reference_id": 6,
@@ -102,11 +85,7 @@
         "total_distance": 10,
         "reverse_delay": 0,
         "delay": {
-            "init_val": {
-                "reference_id": 4,
-                "property": "duration"
-            },
-            "reference_id": 5,
+            "reference_id": 4,
             "property": "duration"
         },
         "loop": true,
@@ -196,22 +175,13 @@
     {
         "id": 17,
         "type": "move",
-        "duration": 516,
-        "total_distance": 400,
-        "ease_in": "cubic",
-        "comment": "bg fever 4 bg move down"
-    },
-    {
-        "id": 18,
-        "type": "move",
-        "duration": 200,
-        "total_distance": 40,
-        "delay": {
-            "reference_id": 17,
-            "property": "duration"
-        },
+        "duration": 716,
+        "total_distance": 360,
         "ease_out": "quadratic",
-        "comment": "bg fever 4 bg move up"
+        "waypoints": [
+            { "at": 516, "value": 400, "ease_in": "cubic" }
+        ],
+        "comment": "bg fever 4 bg move down/up (merged from old ids 17+18)"
     },
     {
         "id": 19,
@@ -247,23 +217,14 @@
     {
         "id": 22,
         "type": "move",
-        "duration": 333,
-        "total_distance": 600,
+        "duration": 499,
+        "total_distance": 500,
         "start_position": -500,
-        "ease_out": "quadratic",
-        "comment": "bg fever 2 move in"
-    },
-    {
-        "id": 23,
-        "type": "move",
-        "duration": 166,
-        "total_distance": 100,
-        "delay": {
-            "reference_id": 22,
-            "property": "duration"
-        },
         "ease_in": "quadratic",
-        "comment": "bg fever 2 move out"
+        "waypoints": [
+            { "at": 333, "value": 600, "ease_out": "quadratic" }
+        ],
+        "comment": "bg fever 2 move in/out (merged from old ids 22+23)"
     },
     {
         "id": 24,