revert: 移除构建期 IME 守卫补丁 — 补丁打在产物上不具持久性

taekchef 的 apply-ime-guard.mjs 在每次 build/prepare/bundle 后把守卫
字符串注入 lib/client.js，但补丁对象是构建产物而非源码：
- 裸 tsdown 重建 / 其他构建路径产出无守卫的 bundle（#562 复发根因）
- 守卫逻辑游离于源码之外，难以测试与维护

运行时方案（src/client/ime-guard.ts + tests/ime-guard.spec.ts）已在
源码内实现同等守卫，经 document capture 覆盖全部劫持路径，任何构建
方式产物都自带守卫。合并远端提交后撤掉构建期补丁，保留运行时方案。

package.json

@@ -51,11 +51,11 @@
     "src"
   ],
   "scripts": {
-    "build": "rm -rf lib && tsc -p tsconfig.build.json && tsdown && node scripts/apply-ime-guard.mjs",
+    "build": "rm -rf lib && tsc -p tsconfig.build.json && tsdown",
     "typecheck": "tsc --noEmit",
-    "bundle": "tsdown && node scripts/apply-ime-guard.mjs",
+    "bundle": "tsdown",
     "watch": "tsdown --watch",
-    "prepare": "tsdown && node scripts/apply-ime-guard.mjs",
+    "prepare": "tsdown",
     "test": "vitest run"
   },
   "license": "MIT",

scripts/apply-ime-guard.mjs

@@ -1,26 +0,0 @@
-// 持久 IME 守卫补丁（2026-08-10，changelog 见 AGENTS.md）：
-// Univer InputNumber 在 document capture 拦截全页 ↑/↓ 且无 isComposing 守卫，
-// 会摧毁中文输入法组合（候选词导航被劫持）。每次 build 后自动重打。
-import { readFileSync, writeFileSync } from 'node:fs'
-import { fileURLToPath } from 'node:url'
-import { dirname, join } from 'node:path'
-
-const root = join(dirname(fileURLToPath(import.meta.url)), '..')
-const target = join(root, 'lib/client.js')
-const src = readFileSync(target, 'utf8')
-
-const pattern = /function handleKeyDown\(e\) \{(\s*)if \(disabled\) return;/
-const guard = 'function handleKeyDown(e) {\n\t\t\t\t\tif (e.isComposing || e.keyCode === 229) return;\n\t\t\t\t\tif (disabled) return;'
-
-if (src.includes('e.isComposing || e.keyCode === 229')) {
-  console.log('[apply-ime-guard] guard already present, skip')
-  process.exit(0)
-}
-const count = src.match(new RegExp(pattern.source, 'g'))?.length ?? 0
-if (count === 0) {
-  console.error('[apply-ime-guard] ERROR: pattern not found in lib/client.js — univer structure may have changed, inspect manually!')
-  process.exit(1)
-}
-const next = src.replace(pattern, guard)
-writeFileSync(target, next)
-console.log(`[apply-ime-guard] injected IME guard (${count} site(s))`)