fix: 修复内存溢出问题，compact 时清理持久增长数据结构

- compact 时清理 contentReplacementState（seenIds/replacements）
- logError() 使用 shortErrorStack 替代完整 err.stack，减少 GC 压力
- permissionDenials 每次 submitMessage 清空，防止无限增长
- SSE 缓冲区添加 1MB 上限，防止畸形数据无限累积

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/utils/log.ts

@@ -17,7 +17,7 @@ import {
 import { CACHE_PATHS } from './cachePaths.js'
 import { stripDisplayTags, stripDisplayTagsAllowEmpty } from './displayTags.js'
 import { isEnvTruthy } from './envUtils.js'
-import { toError } from './errors.js'
+import { toError, shortErrorStack } from './errors.js'
 import { isEssentialTrafficOnly } from './privacyLevel.js'
 import { jsonParse } from './slowOperations.js'
 
@@ -175,7 +175,7 @@ export function logError(error: unknown): void {
       return
     }
 
-    const errorStr = err.stack || err.message
+    const errorStr = shortErrorStack(err)
 
     const errorInfo = {
       error: errorStr,