Playtest #6 fixes: summons placed by hand, boss pool stall, bounties, 联防 leak counter, distinct offers, 机变 card text, phone buy tap, skill triggers, blocking, push force, 孤立, enemies, element bar

- #1 #2 skill / device summons (赫默's drone, 巫恋's doll, 凯瑟琳's devices) are hand cards placed by the player;
  placed summons deploy once at battle start, then a skill summon re-appears at its tile on each cast (the user's call)
- #3 叙拉古 隐匿 ends on time (32 + 0.4 × layers s); 忍冬 S3 迷彩 lasts until her next cast (official), kept apart from 隐匿
- #4 multi-round bounty cards last two battles (the user's call; MULTI_ROUND_BOUNTY_BATTLES), blue / red card text
- #5 the shared boss pool's float dust (≈3.6e-12 HP) stalled Final Assault leaders at 0 %; < 1 HP now clears the pool,
  and the team LP reaching 0 first is a defeat (PRTS)
- #6 #10 机变 cards show their official effect text; an invisible 详情 button no longer swallows the confirming tap on phones
- #7 live ×N counter of a leaker's enemies still on the 联防 field (LP loss stays capped at 10)
- #8 #15 #16 skill triggers per 技能策略: skill-range triggers, injured-ally heals (古米, 塞雷娅), tank take-damage
  triggers with a 3 s cooldown; 新约能天使 S2 shields the highest-aggro operator in range
- #9 official per-enemy model scales (威龙)
- #11 element bar under the unit's HP bar (white = 元素值 left, element-coloured refill after a burst), floor rounding
- #12 枯朽战车 kit per PRTS; every ranged enemy reaches its target's 0.25 collider
- #13 恐惧 wander (萨科塔之翼 at half HP, operator fears make enemies flee) with re-planning after pushes
- #14 push / pull distance by 力度 − 重量 (PRTS table); #17 every blocker attacks what it blocks; ASPD floor 20
- #18 炎佑 is 孤立: no heals or ally buffs
- #19 every free pick-one chess offer (promotion reward, 信标, 寻呼模块) shows different operators
- DESIGN §20 and the normative lines, SIM / META / DATA / PLAYING updated; 2747 unit tests and all 27 browser suites
  green; dev recordings regenerated

server/sim/grid.js

@@ -34,7 +34,8 @@
 // platforms, research 08 §8 #1]) and CRATE (阻隔工事 devices — `setObstacle(r, c, on, 'crate')`: walkable at cost 1000,
 // blocks line of sight; an enemy that must cross one is blocked by the device and breaks it). Any change bumps
 // `version`, which invalidates the cached fields (enemies re-read their next step). `groundPassable` (placement,
-// displacement, content) still treats both kinds as occupied unless `ignoreObstacles`.
+// displacement, content) still treats both kinds as occupied unless `ignoreObstacles`. `straightClear` tells whether an
+// off-centre unit may walk straight to a tile centre (ai.js planLeg, fear.js: else it steps back to its tile centre).
 
 import { ROWS, COLS } from './constants.js';
 
@@ -427,3 +428,27 @@ export function bresenhamTiles(a, b) {
   }
   return out;
 }
+
+/**
+ * Whether a straight move from (x, y) to the centre of tile p = {x: col, y: row} only crosses ground-walkable,
+ * crate-free tiles (the start and end tiles excepted). Exact grid traversal (tile (r,c) spans c ± 0.5, r ± 0.5); a
+ * line through a tile corner needs both side tiles clear (as the grid's Bresenham smoothing).
+ */
+export function straightClear(g, x, y, p) {
+  let c = Math.round(x), r = Math.round(y);
+  const dx = p.x - x, dy = p.y - y;
+  const sc = dx > 0 ? 1 : -1, sr = dy > 0 ? 1 : -1;
+  const ddx = dx !== 0 ? Math.abs(1 / dx) : Infinity, ddy = dy !== 0 ? Math.abs(1 / dy) : Infinity;
+  let tx = dx !== 0 ? (c + 0.5 * sc - x) / dx : Infinity;
+  let ty = dy !== 0 ? (r + 0.5 * sr - y) / dy : Infinity;
+  const clear = (rr, cc) => (rr === p.y && cc === p.x) || (g.walkable(rr, cc) && !(g.obstacle[rr * COLS + cc] & OB_CRATE));
+  for (let guard = 4 * COLS; guard > 0 && (r !== p.y || c !== p.x); guard--) {
+    if (tx >= 1 && ty >= 1) break;
+    if (Math.abs(tx - ty) < 1e-9) {
+      if (!clear(r, c + sc) || !clear(r + sr, c)) return false;
+      c += sc; r += sr; tx += ddx; ty += ddy;
+    } else if (tx < ty) { c += sc; tx += ddx; } else { r += sr; ty += ddy; }
+    if (!clear(r, c)) return false;
+  }
+  return true;
+}