3.10.0 to staging: per-fight difficulty levers, Main quest popup, web gets a horizontal spell strip

Difficulty has new per-fight knobs. Two levers — enemyAggression (whether the enemy pushes toward the player) and enemyInRangeSlotCount (how many enemy units can be in range at once) — are now set per fight in the data file instead of being game-wide. First pass uses them for a difficulty ladder bump (more 3-enemy fights on the main path) paired with eased start fights on both side quests so they're less punishing to attempt. The strange-ruins-entry fight drops its slot-count lever entirely.

Hero-position bias (the heuristic that picks where heroes start on the fight grid) now gates by scene id rather than fight id. The same fight reused across different scenes can get the right starting positions per scene. Already extended down to fights 5–8 (To the Lake and Rose Lake area).

Quest UX is cleaner. A new Main quest popup fires when the main story takes a step — separate from side-quest popups so the player can tell them apart. The story map ticks visited scenes so you can see what you've already walked through. Snake Medallion's quest giver moves to the Library (per #295) and the map's quest-indicator system handles the new location correctly.

Web build picks up a consistent selected-hero position and a horizontal spell strip at the bottom. Desktop play was using the mobile portrait layout — which crammed the spell list into a vertical strip alongside the field — so the horizontal strip uses the wider viewport instead. Selected-hero position is now consistent across both layouts so the highlighted hero card sits in the same relative spot.