Feat/understand api queue

[chenxiaobin-lang]

Description

Support asynchronous processing of understanding api when wait = false

Related Issue

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

• add UnderstandingParseProcessor to queue
• enable asynchronous processing of understanding api when wait=false

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes

[qin-ctx]

这次先发布两条 blocking bug 和一条建议。主要问题是：ExternalParse 把解析延后到队列后，源文件和 watch 生命周期没有一起迁移，导致现有 temp upload 与 watch_interval 场景回归。

[qin-ctx]

补充为行内评论，便于直接定位。两个问题都是 blocking。

[qin-ctx]

这轮继续 REQUEST_CHANGES。PR 目标是让 UnderstandingAPI 的 wait=false 改成 ExternalParse 队列异步处理。旧的 watch、ParserRouter、空 root_uri、reason memory 的部分问题已经有进展，但当前还剩几个 blocking 回归：默认 telemetry 场景 task 会提前完成；MCP temp upload 仍会把即将删除的路径写进队列；resource reservation 用 exact lock 破坏原有 tree-lock 语义；lock handoff retry 会卡住队列 in_progress；启动恢复消息可能在 memory link service 完成依赖注入前被消费。