fix(context): 细化 micro compact 保留策略

[Yumiue]

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概要

本 PR 修复并细化了上下文微压缩（micro compact）的保留策略，解决三个问题：

1. 缺少专用摘要器的工具结果被静默清空

summarizeOrClear 在遇到未注册摘要器的工具时直接返回清空消息，导致历史信息丢失。现在会退化为最小可读摘要 [summary] toolName lines=N chars=M，保证工具执行历史始终有可见痕迹。

2. 文件操作 pin 判定覆盖不足

• 新增 CopyFile / MoveFile 到默认 pin 工具列表
• pin 路径匹配从单一字段扩展为多候选顺序检查：relative_path → path → source_path → destination_path，防止复制/移动操作的文件被过早回收

3. 工具输出截断丢弃尾部关键信息

原来的单点截断（仅保留前 600 字符）可能导致错误日志、堆栈信息等尾部关键内容丢失。改为头尾窗口保留（各 300 字符），中间用 ...[truncated]... 标记，确保 memo 提取时兼顾上下文与错误定位。

附带变更

• ReadTool / SpawnSubagent 的 MicroCompactPolicy 调整为 Compact，避免其历史被无条件保留
• projectedToolMetadataAllowlist 新增 source_path / destination_path 字段

测试

• go build ./... 通过
• go test ./internal/context/... 全部通过
• 17 文件，+427 / -75

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[fennoai]

Found 2 noteworthy issues after code quality, performance, security, and documentation passes.

[fennoai]

medium Adding source_path / destination_path to the projected metadata allowlist makes copy/move tool messages send absolute local filesystem paths back to the provider. filesystem_copy_file and filesystem_move_file currently persist src/dst as absolute paths, so this change leaks workspace layout and usernames into recent-window / memo-extraction context. Please normalize these fields to workspace-relative paths before allowlisting them, or keep them out of model-visible metadata.

[fennoai]

medium Switching codebase_read from PreserveHistory to Compact is a behavior change that drops previously-read source bodies down to path/line-count summaries. That is at odds with the current repository design contract (docs/repository-design.md, acceptance criterion 28), which explicitly relies on codebase_read being the implementation-bearing tool that stays available across compact while codebase_search_* can be summarized. If this policy change is intentional, the surrounding docs/prompt contract should be updated in the same PR; otherwise this weakens the "must verify via codebase_read" workflow.

[codecov]

Codecov Report

❌ Patch coverage is 79.31034% with 18 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
internal/context/projection.go	66.66%	7 Missing and 3 partials ⚠️
internal/context/microcompact.go	71.42%	4 Missing and 4 partials ⚠️

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