chore: 移除 cachedMCConfig stub 及 prompts.ts 的 CACHED_MICROCOMPACT 死代码

- 删除 src/services/compact/cachedMCConfig.ts（自动生成的 stub）
- 同步移除 src/constants/prompts.ts 中依赖该 stub 的代码：
  - getCachedMCConfigForFRC 变量（feature('CACHED_MICROCOMPACT') 守卫的 require）
  - getFunctionResultClearingSection 函数（约 18 行）
  - systemPrompt 数组中的 frc section 调用与注册

CACHED_MICROCOMPACT 不在 build.ts DEFAULT_BUILD_FEATURES 也不在 dev 默认列表，所有默认配置下整段为构建期死代码。

Co-Authored-By: glm-5.2 <zai-org@claude-code-best.win>

src/constants/prompts.ts

@@ -67,12 +67,6 @@ import { getCurrentMode } from 'src/modes/store.js'
 
 // Dead code elimination: conditional imports for feature-gated modules
 /* eslint-disable @typescript-eslint/no-require-imports */
-const getCachedMCConfigForFRC = feature('CACHED_MICROCOMPACT')
-  ? (
-      require('../services/compact/cachedMCConfig.js') as typeof import('../services/compact/cachedMCConfig.js')
-    ).getCachedMCConfig
-  : null
-
 const proactiveModule =
   feature('PROACTIVE') || feature('KAIROS')
     ? require('../proactive/index.js')
@@ -454,7 +448,6 @@ ${CYBER_RISK_INSTRUCTION}`,
         ? null
         : getMcpInstructionsSection(mcpClients),
       getScratchpadInstructions(),
-      getFunctionResultClearingSection(model),
       SUMMARIZE_TOOL_RESULTS_SECTION,
       getProactiveSection(),
     ].filter(s => s !== null)
@@ -492,7 +485,6 @@ ${CYBER_RISK_INSTRUCTION}`,
       'MCP servers connect/disconnect between turns',
     ),
     systemPromptSection('scratchpad', () => getScratchpadInstructions()),
-    systemPromptSection('frc', () => getFunctionResultClearingSection(model)),
     systemPromptSection(
       'summarize_tool_results',
       () => SUMMARIZE_TOOL_RESULTS_SECTION,
@@ -781,26 +773,6 @@ Only use \`/tmp\` if the user explicitly requests it.
 The scratchpad directory is session-specific, isolated from the user's project, and can be used freely without permission prompts.`
 }
 
-function getFunctionResultClearingSection(model: string): string | null {
-  if (!feature('CACHED_MICROCOMPACT') || !getCachedMCConfigForFRC) {
-    return null
-  }
-  const config = getCachedMCConfigForFRC()
-  const isModelSupported = config.supportedModels?.some(pattern =>
-    model.includes(pattern),
-  )
-  if (
-    !config.enabled ||
-    !config.systemPromptSuggestSummaries ||
-    !isModelSupported
-  ) {
-    return null
-  }
-  return `# Function Result Clearing
-
-Old tool results will be automatically cleared from context to free up space. The ${config.keepRecent} most recent results are always kept.`
-}
-
 const SUMMARIZE_TOOL_RESULTS_SECTION = `When working with tool results, write down any important information you might need later in your response, as the original tool result may be cleared later.`
 
 function getBriefSection(): string | null {

src/services/compact/cachedMCConfig.ts

@@ -1,8 +0,0 @@
-// Auto-generated stub — replace with real implementation
-export {}
-export const getCachedMCConfig: () => {
-  enabled?: boolean
-  systemPromptSuggestSummaries?: boolean
-  supportedModels?: string[]
-  [key: string]: unknown
-} = () => ({})