Playtest #4 fixes: tile picking, knocked-down state, element gauges, draft timer, live stats, shop items, drones, 赫默, 炎佑, UI flash

- #1 picking by the tile under the pointer (prep, battle, pen, equipment drops); the dragged model stays
  under the pointer (mouse and touch); pixel probe removed; phone ghost-click on the underframe fixed
- #2 two-tap confirm on 机变 cards (like the shop)
- #3 a 同盟 room with one human is untimed like 独立模拟 (no countdown outside battles)
- #4 strategy draft: one synced countdown, 30 s per human turn, timeout takes the highlighted band
- #5 special 维式重锤 (4) and 突变细胞 no longer sold; item card shows where they come from
- #6 operator skill-mode sounds no longer play on normal attacks (纯烬艾雅法拉 and 55 others)
- #7 detail card shows live battle stats and the prep-time battle-start stats (g.unitStats)
- #8 official element gauges on units; burst cooldown (阻回) per PRTS
- #9 knocked-down operators stay on their tile with a redeploy countdown ring
- #10 drone behaviour per PRTS (暴鸰, 先兆者 shells, 黑云, 萨科塔之眼)
- #11 赫默's drone only from her skill; placeable summons limited to talent tokens
- #12 炎佑 stays where it is with no enemies; 祛恶之焰 as a continuous channel
- #13 the occasional giant bond icon (loading texture scaled ×46) fixed
- docs (DESIGN §18), recordings, data and tests updated (2467 unit tests, all browser suites green)

docs/ASSETS.md

@@ -149,6 +149,10 @@ All paths are URL paths relative to the site root, for example `/assets/char/ava
       units:  { [charId|tokenId|enemyId]: { attack?, hit?, skill?, skills?: {[skillIndex]: url}, die?, born? } }
     }
   },
+  // units' attack / hit (tools/assets/audio.mjs pickUnitSfx): operators get normal-mode banks only — the plain
+  // `attack` / `combat` ability first, never a bank holding a skill-mode file (`_d` / `_h` / `_s`; the normal attack's end
+  // in `_n`) — with their own projectile banks (ON_PROJECTILE_BORN / _HIT.projectile_chr_<name>) as fallbacks
+  // (DESIGN §18.4: 纯烬艾雅法拉's S3 impact used to be her `hit`); enemies and tokens take the first attack-like bank
   fonts: { css: '/fonts/fonts.css', faces: { [name]: { family, weight, woff2?, original } } }
 }
 ```