refactor: 移除 context-mode，Chrome 快照改为直接返回

context-mode 的 ctx_execute 系工具以真实 shell 执行且权限为 allow，绕过了
bash 策略与 protectedWrites；其每轮注入、独立 MCP 子进程与 skills 也与组合包
提示词单一所有权冲突。大输出职责已由 pi-overflow（入口截断）与
pi-compaction（压力遮蔽）承担：
- 删除 context-mode 依赖、wrapper/过滤器、skills，以及 ctx_* 的权限、
  tools.jsonc、路由规则、tool-search 常驻与 4 个分组
- better-sqlite3@12 仅为 context-mode 传递依赖，随之移除根 allowScripts
- pi-chrome：按用户决定移除快照隐私规则与 .pi/chrome-context 临时文件机制，
  快照 JSON 直接作为工具结果返回、details 只留小型元数据，超长由 pi-overflow
  截断并用 overflow_query 提取；授权生命周期不变

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pi-compaction/README.md

@@ -16,7 +16,7 @@ Additionally it:
 - publishes one effective-context snapshot for normal provider requests and Codex/SubAPI native compaction;
 - maintains a masked-results ledger so `/context`, `/compaction-status`, the footer, and AutoReview see the same placeholders the model sees.
 
-Context Mode remains responsible for preventing large external data from entering the session. RTK remains responsible for ordinary tool-output cleanup.
+pi-overflow bounds new tool results as they arrive. RTK remains responsible for ordinary tool-output cleanup.
 
 ## Configuration