test: cover message identity compatibility across SDKs

[cschleiden]

The runtime now exposes one stable user-message UUID across SendResult.messageId, visible queue.pendingItems rows, and user.message events. With @github/copilot 1.0.83-2 pinned on main, all six SDKs generate the optional identity fields from the canonical schemas; this PR adds compatibility coverage to prevent wire-name or older-runtime regressions.

This change:

• covers QueuePendingItems.messageId and UserMessageData.messageId in Node, .NET, Python, Go, Rust, and Java
• verifies the camelCase wire name in serialization and deserialization paths where applicable
• verifies payloads from older runtimes remain valid when messageId is absent
• drops the former Rust-only schema augmentation approach in favor of the normal deterministic generators

Validation:

• shared TypeScript, C#, Python, Go, and Rust codegen, with no generated diff
• Java Maven codegen, with no generated diff
• full Node format, lint, typecheck, build, and test suite
• full Python format, lint, typecheck, and test suite
• go test ./...
• full .NET test project
• mvn verify
• Rust format, Clippy, and all-feature tests

[Copilot]

Copilot review overview

🟡 Changes recommended

Adding a field to the stable public UserMessageData struct introduces an unresolved Rust source-compatibility break.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Review tier: Balanced
Findings: 1

New issues introduced by this change (1)

Severity	Finding
	scripts/​codegen/​rust.ts — Injecting this field into UserMessageData is a Rust source-breaking API change: the type is…

What changed in this PR

Exposes stable queued-message UUIDs in Rust for correlating send results, queue entries, and user-message events.

Changes:

• Adds temporary Rust codegen schema bridges for messageId.
• Regenerates Rust API/event types with optional message IDs.
• Adds serde compatibility tests for current and legacy payloads.

File	Description
scripts/​codegen/​utils.ts	Adds schema augmentation helpers.
scripts/​codegen/​rust.ts	Applies augmentations during Rust generation.
rust/​src/​generated/​api_types.rs	Exposes queue-item message IDs.
rust/​src/​generated/​session_events.rs	Exposes user-event message IDs.
rust/​tests/​api_types_test.rs	Tests queue-item serde behavior.
rust/​tests/​session_events_test.rs	Tests event-payload serde behavior.

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[SteveSandersonMS]

Thanks for addressing the real correlation gap: callers need one stable message UUID shared by SendResult.messageId, pending queue rows, and user.message events.

Suggested scope and timing:

• Since this capability is language-neutral, it would be best for the SDK exposure to cover all six languages (Node, C#, Python, Go, Rust, and Java).
• The corresponding fields are not yet present in the currently pinned runtime schema. To keep the SDK aligned with the shipped runtime contract, I suggest waiting for those fields to land, then regenerating the affected SDKs through the normal code-generation pipeline and adding focused compatibility tests for each language as appropriate.

For tracking, I've moved this to draft - please mark it ready to review when the runtime fields have landed and the six SDKs are generated from the updated contract.

[cschleiden]

The runtime fields are now available through the pinned @github/copilot 1.0.83-2 schemas. I rebased onto current main, removed the temporary Rust-only augmentation, added compatibility coverage for all six SDKs, and completed the full validation set, so this is ready for review.