chore: decouple Rust SDK from dstack core workspace

[kvinwang]

Summary

The public Rust SDK (dstack-sdk / dstack-sdk-types) only talks to guest-agent over the wire. It is not a library dependency of the core dstack/ crates, but it was listed as a workspace member, which forced every Yocto guest build to rsync sdk/rust just so Cargo could resolve the workspace.

This PR splits the SDK into its own Cargo workspace so core builds no longer need that tree.

Changes

• sdk/rust is now a standalone workspace (dstack-sdk, dstack-sdk-types, no_std_check) with its own Cargo.lock
• remove ../sdk/rust members and dstack-sdk-types from dstack/Cargo.toml
• move no_std_check next to the SDK types it validates
• dstack-guest.bb only stages dstack/ + rootfs (no SDK rsync)
• SDK CI (sdk.yaml) and crates.io publish use --manifest-path sdk/rust/Cargo.toml

CI coverage (preserved)

Check	Where
Multi-language SDK suite (sdk/run-tests.sh)	SDK tests workflow
dstack-sdk-types unit + no_std_test	sdk/run-tests.sh + sdk.yaml
WASM dstack-sdk-types	sdk.yaml (wasm32-unknown-unknown)
no_std_check on thumbv6m-none-eabi	sdk.yaml
Core clippy / fmt / run-tests.sh	unchanged Rust checks (no longer pulls SDK)

Local verification

• cargo check -p dstack-guest-agent in an isolated dstack/ tree without sdk/ present
• cargo check -p dstack-sdk / cargo test -p dstack-sdk-types under sdk/rust
• WASM + thumbv6m-none-eabi checks for SDK types / no_std_check

Test plan

• isolated dstack guest-agent build without sdk sibling
• sdk workspace tests and no_std/WASM targets
• CI: Rust checks + SDK tests on this PR

[Copilot]

Pull request overview

This PR decouples the public Rust SDK (sdk/rust) from the core dstack/ Cargo workspace so core builds (notably Yocto guest builds) no longer need to stage the SDK tree just for workspace resolution.

Changes:

• Create a standalone Cargo workspace under sdk/rust (including dstack-sdk, dstack-sdk-types, and no_std_check) with its own Cargo.lock.
• Remove SDK crates from the core dstack/ workspace and stop Yocto guest builds from rsync’ing sdk/rust.
• Update CI/release automation to use --manifest-path sdk/rust/Cargo.toml for SDK checks and publishing.

Reviewed changes

Copilot reviewed 9 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
sdk/rust/Cargo.toml	Defines the new standalone SDK workspace and centralizes dependency versions.
sdk/rust/Cargo.lock	Adds an SDK-specific lockfile for the standalone workspace.
sdk/rust/types/Cargo.toml	Removes linkage to the core workspace so types are resolved via the SDK workspace.
sdk/rust/no_std_check/Cargo.toml	Marks the check crate as non-publishable and ties it to workspace deps.
sdk/rust/no_std_check/src/lib.rs	Adds a minimal #![no_std] compile check that imports dstack-sdk-types.
sdk/rust/README.md	Documents that sdk/rust is now a standalone Cargo workspace.
dstack/Cargo.toml	Removes SDK members and the dstack-sdk-types workspace dependency from core.
dstack/Cargo.lock	Regenerates lockfile after removing SDK crates from the core workspace graph.
os/yocto/layers/meta-dstack/recipes-core/dstack-guest/dstack-guest.bb	Stops staging sdk/rust into the Yocto guest build source tree.
.github/workflows/sdk.yaml	Updates SDK validation commands to target sdk/rust/Cargo.toml.
.github/workflows/rust-sdk-release.yml	Updates version checks to look at the SDK workspace instead of core workspace deps.
.github/scripts/cargo-publish-idempotent.sh	Publishes SDK crates using the SDK workspace manifest path.

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