feat(cloud): expose steering controls for cloud sessions

[tatoalo]

Problem

Cloud sessions do not expose the steering controls available to negotiated native runs.

Changes

Enables cloud Steer/Queue controls and shortcuts when native steering is supported.

[tatoalo]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(cloud): expose steering controls for cloud sessions #3541 👈 (View in Graphite)
• fix(cloud): hydrate resumed transcripts atomically #3540
• fix(cloud): reconcile resumed events by leaf identity #3539
• feat(cloud): negotiate idempotent steer delivery #3538
• feat(cloud): add native steering to agent adapters #3537
• main

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit c22ad61.}

[posthog]

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If these changes are unexpected, they may be caused by a flaky test or a broken snapshot on master. Don't approve — rerun the job or wait for a fix.

[stamphog]

The new cloud native-steer code path is dead code: sessionSupportsNativeSteer in @posthog/shared/src/sessions.ts hard-returns false for any session where isCloud === true (line 234), so the new if (session.isCloud) { return sendCloudPrompt(..., { steer: true }) } block inside if (sessionSupportsNativeSteer(session)) can never be reached. The accompanying test "sends a native cloud steer immediately" would also fail in CI for the same reason — the expected steer: true param is never sent.