fix(ipc): use named FIFOs for task communication on Unix

[wan9chi]

Motivation

Codex CLI's and Claude Code's default sandboxes block Unix domain sockets, so vp run fails while setting up task communication before any task code runs (#562). Named FIFOs are plain files, and both sandboxes allow them.

This PR reapplies the FIFO transport from #565 with a rename, a review pass, and new coverage:

• The crate is pipe_socket: socket-style server-client IPC, implemented on named pipes rather than Unix domain sockets. It carries no task-runner specifics, so it sits outside the vite_* prefix, like fspy and pty_terminal. It exposes Server::bind, Server::name, Server::accept, and Client::connect; FIFOs on Unix and named pipes on Windows stay implementation details.
• Client::connect now fails instead of hanging when the server is gone. The rendezvous open is nonblocking, so a missing reader turns into a connection-refused error at once. While waiting for the server's ready byte, the client watches the rendezvous write end and probes the server every 100ms; a dead server turns into an error within one probe interval. macOS needs the probe because its poll does not always report FIFO events; Linux reports the death at once. The module documents the handshake step by step.
• A new integration test pins the no-hang behavior for both cases: server gone before the connection attempt, and server dying in the middle of one.
• The Codex sandbox snapshot now records the end state this PR and fix(fspy): unify shared memory on a sparse temp file across all platforms #576 were built for: the task runs inside the sandbox, fspy traces its reads, and editing the traced file causes a cache miss on the next run. Regenerated against the real codex CLI on macOS. The Claude sandbox snapshot is carried over from fix(ipc): use named FIFOs on Unix #565 unchanged; it needs an srt binary to regenerate, and the recorded behavior does not depend on the shared-memory backend that changed underneath it.

Closes #562.

🤖 Generated with Claude Code

[wan9chi]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• fix(ipc): use named FIFOs for task communication on Unix #569 : 2 dependent PRs (#577 , #586 ) 👈 (View in Graphite)
• fix(fspy): unify shared memory on a sparse temp file across all platforms #576
• main

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[github-actions]

fspy benchmark

linux

dynamic/launch             change  +1.83%  [ -5.39% .. +10.42%]  overhead   +54.53%
dynamic/access             change  +0.54%  [ -5.20% ..  +7.01%]  overhead   +49.93%
static/launch              change  +1.86%  [-11.53% .. +13.77%]  overhead  +167.30%
static/access              change  -1.14%  [-14.09% ..  +6.09%]  overhead  +827.60%

macos

dynamic/launch             change  +0.16%  [ -5.32% ..  +5.64%]  overhead  +224.73%
dynamic/access             change  +0.00%  [ -6.27% ..  +9.40%]  overhead   +22.99%

windows

dynamic/launch             change  -0.17%  [ -4.72% ..  +4.12%]  overhead   +28.81%
dynamic/access             change  +0.17%  [ -1.42% ..  +1.23%]  overhead    +8.23%

[wan9chi]

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[chatgpt-codex-connector]

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