Introduces:
- src/shared/process-stream-reader.ts: Buffer-concat stream reader compatible with both Bun and Node ChildProcess stdout (replaces Web Response API usage)
- src/tools/shared/search-process-output.ts: structured subprocess output collector with timeout, kill, and rejection cleanup
- bun-spawn-shim hardened: Node path forces windowsHide: true; spawn errors no longer escape as unhandledRejection
Foundation for #3919 fix.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
YeonGyu-Kim