Test extension canvas forwarding

[jmoseley]

A canvas registration regression in Copilot CLI 1.0.76-5 initially appeared to originate in the SDK extension path. The investigation confirmed that joinSession({ canvases }) forwards canvas providers correctly; the actual failure is an agent-runtime connection identity race.

This adds focused coverage for the SDK boundary so future regressions cannot silently drop canvases before resumeSessionForExtension.

This PR is test-only and does not fix the runtime issue. The production fix belongs in copilot-agent-runtime, where extension identity must be published before the first JSON-RPC request is dispatched. Runtime PR github/copilot-agent-runtime#13958 implements that ordering.

[Copilot]

🟢 Ready to approve

The focused test accurately validates the documented SDK boundary behavior.

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Pull request overview

Adds focused regression coverage confirming extension sessions forward canvas providers to resumeSessionForExtension.

Changes:

• Creates a canvas provider in the extension test.
• Verifies joinSession forwards it unchanged.

File summaries

File	Description
nodejs/test/extension.test.ts	Adds canvas-forwarding regression coverage.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Balanced

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[github-actions]

Cross-SDK Consistency Review ✅

This PR is test-only — it adds a single regression test in nodejs/test/extension.test.ts to confirm that joinSession({ canvases }) correctly forwards canvas providers to resumeSessionForExtension.

No production API surface is added or changed. No cross-SDK consistency issues are introduced. Other SDKs do not need corresponding updates.

Generated by SDK Consistency Review Agent for #2185 · sonnet46 15.4 AIC · ⌖ 5.37 AIC · ⊞ 6.6K · ◷

[jmoseley]

Closing because this test only covers the SDK forwarding boundary and would not catch the agent-runtime registration race. The regression coverage and fix belong in copilot-agent-runtime.