guest-agent: remove EmitEvent API

[kvinwang]

Summary

Remove the guest-agent EmitEvent RPC and matching SDK wrappers.

• Not portable across TEEs: the API is TDX-centric (extend RTMR3). Other platforms and the guest-agent simulator cannot implement it faithfully.
• Rare real-world use: applications almost never need app-level RTMR extension via the socket API; boot measurements already go through emit_runtime_event inside dstack-util.
• Simulator / multi-TEE friction: the simulator could only refuse the call, which made SDK demos and tests awkward and encouraged a TDX-only surface on a multi-TEE stack.

Boot-time RTMR/PCR extension via dstack_attest::emit_runtime_event (used by dstack-util system setup) is unchanged. Apps that still need extra runtime measurements should use native TDX/TSM measurement interfaces and own their event-log story.

Changes

• Proto: drop rpc EmitEvent and EmitEventArgs
• guest-agent / simulator: drop PlatformBackend::emit_event and RPC handler
• SDKs: remove emit_event / EmitEvent / emitEvent from Rust, Python, Go, JS
• Docs: curl API, native TEE interfaces, security model, SDK READMEs

Test plan

• cargo test -p dstack-guest-agent -p dstack-guest-agent-simulator (26 tests pass)
• cargo check -p dstack-guest-agent -p dstack-guest-agent-simulator -p dstack-sdk
• cargo fmt --check
• go build ./dstack/ in sdk/go
• Confirm no remaining production callers of /EmitEvent (expected: none or rare)

[Copilot]

Pull request overview

Removes the guest-agent EmitEvent RPC and all corresponding SDK wrappers and documentation, aligning the public surface area with a multi-TEE design and avoiding a TDX-centric runtime-measurement API.

Changes:

• Deleted EmitEvent from the guest-agent proto/service and removed backend + RPC handler plumbing (including simulator behavior/tests).
• Removed emit_event / EmitEvent / emitEvent from Rust, Python, Go, and JS SDKs (plus examples and SDK docs).
• Updated security and native-interface docs (and curl API docs) to reflect that runtime measurements should be done via native TDX/TSM interfaces.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
sdk/rust/src/dstack_client.rs	Removes Rust SDK emit_event wrapper calling /EmitEvent.
sdk/rust/README.md	Removes Rust SDK documentation for event emission.
sdk/rust/examples/dstack_client_usage.rs	Removes emit-event usage from example flow.
sdk/python/tests/test_typing.py	Updates typing expectations to drop emit_event.
sdk/python/tests/test_client.py	Removes emit_event tests and simulator-specific behavior assertions.
sdk/python/src/dstack_sdk/dstack_client.py	Removes async + sync emit_event client methods.
sdk/python/README.md	Removes Python docs and feature-matrix entry for emit_event.
sdk/js/src/index.ts	Removes JS SDK emitEvent implementation.
sdk/js/README.md	Removes JS docs and feature-matrix entry for emitEvent.
sdk/go/README.md	Removes Go SDK event logging documentation and API reference for EmitEvent.
sdk/go/dstack/client.go	Removes Go SDK EmitEvent method implementation.
sdk/curl/api.md	Removes /EmitEvent endpoint docs and renumbers subsequent sections.
guest-agent/src/rpc_service.rs	Drops EmitEvent RPC handler and associated state/backends wiring.
guest-agent/src/backend.rs	Removes PlatformBackend::emit_event and RealPlatform implementation.
guest-agent/rpc/proto/agent_rpc.proto	Deletes rpc EmitEvent and EmitEventArgs message from the service definition.
guest-agent-simulator/src/main.rs	Removes simulator-side emit_event rejection and its test; cleans imports accordingly.
dstack-attest/src/lib.rs	Updates concurrency docs to remove reference to concurrent emit_event RPC calls.
docs/security/security-model.md	Updates security-model narrative to remove “application-emitted events” from RTMR3 description.
docs/native-tee-interfaces.md	Updates guidance to steer apps toward native measurement interfaces instead of /EmitEvent.

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