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)

test/ui/leftovers.e2e.test.js

@@ -256,9 +256,10 @@ describe('client leftovers — real server', { skip: !ENABLED && 'set SP_E2E=1 (
 
       const itemsOf = () => c.page.evaluate((uid) => (globalThis.__SP__.store.get().match.private.board.find((p) => p.uid === uid)?.items || []).map((x) => ({ uid: x.uid, id: x.id })), unit.uid);
       const handItem = async (id) => (await c.handPieces('item')).find((p) => p.id === id) || null;
+      // an item goes to the unit on the tile it is dropped on (user playtest #4 item 1): the operator's own tile
       const dropItem = async (it) => {
-        for (const at of [0.5, 0.35, 0.7]) {
-          await c.drag(await c.piecePoint(it.uid, 0.5), await c.piecePoint(unit.uid, at));
+        for (let i = 0; i < 2; i++) {
+          await c.drag(await c.piecePoint(it.uid, 0.5), await c.tilePoint(tile.row, tile.col));
           await sleep(500);
           if (await c.exists('.eqr') || !(await handItem(it.id))) return;
         }