content: regenerate Season 1 with a gentle onboarding difficulty curve

Generator: raise the early bot-win-rate floor to ~0.97 (near-guaranteed first
stages), widen the early move-buffer margin, and delay score-chase/line-sprint
objectives until stage 9/13 so the opening stretch is pure clear-a-gem. Result:
stage 1 now 16 moves (was 11), stages 1-9 all simple gems at 90-99% bot win.
Preserves theme.bgm=season_001; manifest SHA regenerated. Settings tag -> build 4.

content/season_001/spec.json

@@ -2,7 +2,7 @@
   "seasonId": "season_001",
   "version": 1,
   "title": { "en": "First Bloom", "ko": "첫 개화" },
-  "theme": { "tileSet": "spring", "background": "background.webp" },
+  "theme": { "tileSet": "spring", "background": "background.webp", "bgm": "season_001" },
   "stageCount": 60,
   "baseSeed": 20260611,
   "runsPerStage": 80,