Update close stdin logic

[dmcgowan]

Rework host-side stdin handling so buffered stdin is fully drained
before EOF is delivered, mirroring the containerd runc shim's FIFO
write-reference protocol: closing the client's write end alone is a
detach, and only CloseIO delivers EOF. Fixes truncation seen in the
LargeStdioRoundTrip conformance test and enables stdin detach/re-attach.

On Windows, named pipes lack a second-writer reference, so the same
contract is provided by reconnecting to the stdin pipe on client
disconnect until CloseIO fires.

shimtest update includes attach/detach to validate this change, currently failing with nerdbox

[Copilot]

Pull request overview

This PR updates nerdbox’s shim-side stdin/stdio handling to ensure stdin is fully drained before delivering EOF, aligning behavior with containerd’s shim FIFO write-reference protocol (detach vs. CloseIO), including Windows named-pipe semantics. It also vendors an updated shimtest to validate attach/detach behavior and adds the missing task v2 API for version-aware task client dispatch.

Changes:

• Reworked shim IO forwarding so EOF is delivered via in-band CloseWrite after draining buffered stdin, and ioShutdown safely releases stdin references and waits for stdin draining when possible.
• Implemented Windows stdin detach/re-attach behavior by reconnecting to the stdin named pipe until CloseIO, plus added unit tests for the reconnection contract.
• Updated vendored shimtest (v0.3.3) and introduced version-aware task client selection (v2 vs v3), plus vendored the containerd task v2 API.

Reviewed changes

Copilot reviewed 7 out of 28 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
internal/shim/task/service.go	Adds exec-start failure cleanup to avoid IO shutdown hangs; refines CloseIO stdin semantics commentary.
internal/shim/task/io.go	Integrates new copyStreams return values; releases stdin write reference during shutdown and optionally waits for stdin drain.
internal/shim/task/io_copystreams_unix.go	Changes stdin FIFO EOF/detach behavior by holding a shim write reference and only dropping it on CloseIO/shutdown; returns stdinDone.
internal/shim/task/io_copystreams_windows.go	Implements stdin detach/re-attach by redialing named pipes until stdinEOF is requested; returns stdinDone.
internal/shim/task/io_copystreams_windows_test.go	Adds Windows-only unit tests validating detach/re-attach and EOF delivery behavior.
vendor/github.com/containerd/shimtest/*	Updates conformance/bench suites to use version-aware task clients; adds stdin detach/re-attach conformance test and v2/v3 bridge client.
vendor/github.com/containerd/containerd/api/runtime/task/v2/*	Vendors containerd task v2 protobuf API needed for shimtest’s v2 bridge client.
vendor/modules.txt	Updates vendored module list for new shimtest version and task v2 API path.
go.mod / go.sum	Bumps github.com/containerd/shimtest dependency to v0.3.3.

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[austinvazquez]

Closes #246

[Copilot]

Pull request overview

Copilot reviewed 7 out of 28 changed files in this pull request and generated no new comments.