Recover exec process stdin writes

[jif-oai]

Summary

Remote stdio MCP servers send tool calls by writing JSON-RPC bytes through process/write.

When the exec-server websocket drops at the wrong time, the remote process can survive session recovery, but the stdin write can still fail back to RMCP as a transport send error. RMCP then closes the stdio MCP transport, so tools like node_repl are lost even though the process/session recovery path is working.

This changes process/write to be safe to retry across exec-server recovery:

• adds a required writeId to process/write
• retries remote Session::write with the same writeId after reconnect
• remembers accepted write ids per process so duplicate retries return Accepted without writing the same bytes to child stdin again
• covers both the client retry path and server-side write id dedupe with tests

In simple terms:

before:
write to MCP stdin -> websocket closes -> write errors -> RMCP closes node_repl

after:
write to MCP stdin -> websocket closes -> reconnect -> retry same writeId
server either writes once or recognizes it already did

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: ff17d0ebd0

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".