Handle late cross-kind command failures

[Juns-g]

Problem

Some providers emit commandExecution/completed, then report the same call ID again as a failed generic toolCall. The second terminal event currently throws Cannot merge command with tool-call, so one record can make the thread timeline return 500.

Fix

• keep the finalized command row and its command-specific fields
• merge only the late error's output, completion time, and status
• retain strict kind checks for non-finalized calls and existing dedupe for non-error terminal events

Verification

• pnpm exec turbo run test --filter=@bb/thread-view --force (372 tests)
• pnpm exec turbo run typecheck --filter=@bb/thread-view --force
• Prettier and git diff --check

AGENT GENERATED: by GPT-5