fix(vscode): stop flashing interruption warning on queued follow-up handoff

[marius-kilocode]

Sending a follow-up message while a session is still running queues the prompt behind the active turn. The active turn then breaks out of its loop after the current LLM step drains so the queued prompt can take over. That deliberate handoff was recorded with the turn close reason "interrupted", and the webview renders a yellow "Turn interrupted." warning card whenever a session sits idle with that close reason. Between the old turn closing and the queued turn starting there is a brief idle window, so the card flashed on screen and vanished again, suggesting a premature stop that never happened.

The queue handoff now publishes a dedicated "superseded" close reason instead of "interrupted":

• The turn-close event schema gains the new literal and the prompt loop records it on the handoff break. Memory digests still treat the cut-short turn as interrupted, and attention sounds plus the TUI indicator are unaffected (they key off "completed" and MessageAbortedError respectively).
• The extension and webview extend their close-reason unions, and the webview terminal-state logic returns no warning for superseded turns. The follow-up turn closes with its own reason right after, so no state lingers.
• Real interruptions (Esc, cancel) still close as "interrupted" and still surface the warning.

Covered by a new backend integration test that queues a follow-up mid-turn against a held-open mock LLM stream and asserts both close reasons, plus a webview unit test for the superseded terminal state.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Files Reviewed (11 files)

• .changeset/superseded-turn-close.md
• packages/kilo-vscode/src/kilo-provider-utils.ts
• packages/kilo-vscode/tests/unit/session-outcome.test.ts
• packages/kilo-vscode/webview-ui/src/context/session-outcome.ts
• packages/kilo-vscode/webview-ui/src/types/messages/sessions.ts
• packages/opencode/src/kilocode/memory/turn.ts
• packages/opencode/src/kilocode/session/event.ts
• packages/opencode/src/session/prompt.ts
• packages/opencode/test/kilocode/session-prompt-queue.test.ts
• packages/sdk/js/src/v2/gen/types.gen.ts
• packages/sdk/openapi.json (generated drift, unrelated to this change)

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_{Review guidance: REVIEW.md from base branch main}