feat(sdk-rust): add injection mode parity for send + websocket payloads

[barryonthecape]

Summary

Bring Rust SDK into parity with the recently merged send-mode changes:

• add MessageInjectionMode (wait|steer) enum
• include optional injection_mode in MessageWithMeta
• include optional injection_mode in WS MessageEventPayload
• extend PostMessageRequest with optional mode
• keep send(...) backward-compatible while defaulting to wait
• add send_with_mode(...) for explicit steer/wait requests
• export MessageInjectionMode from crate root
• add parity tests for default wait mode, explicit steer mode, and WS payload parsing

Validation

• cd packages/sdk-rust && cargo test
• all tests passed (unit + parity + doc tests)

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[github-actions]

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[devin-ai-integration]

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[Copilot]

Pull request overview

Adds injection-mode (wait/steer) support to the Rust SDK so REST send/WS payloads match the server and other SDKs.

Changes:

• Introduces MessageInjectionMode enum and threads injection_mode through message response/event types.
• Extends PostMessageRequest with optional mode, updates AgentClient::send to default to wait, and adds send_with_mode.
• Adds parity tests covering default wait, explicit steer, and WS payload deserialization.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
packages/sdk-rust/tests/parity.rs	Adds parity tests for default/explicit injection mode and WS parsing.
packages/sdk-rust/src/types.rs	Defines MessageInjectionMode; adds injection_mode/mode fields to relevant types.
packages/sdk-rust/src/lib.rs	Re-exports MessageInjectionMode from the crate root.
packages/sdk-rust/src/agent.rs	Defaults send() to wait via new send_with_mode() API and forwards mode to the request.

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[barryonthecape]

Great catch — fixed in b089e70. send_with_mode now requires a non-optional MessageInjectionMode and always serializes the mode field explicitly. Re-ran cargo test for sdk-rust (all passing).