Timeline command components crash on unexpected payload shapes

Nobody has claimed this yet.

Several timeline command components assume specific payload shapes and will throw if the data doesn't match. An error boundary was added in #1598 to prevent these from crashing the app, but the components themselves should add defensive guards.

Vulnerable components:
- **`AsyncStorageMutationCommand`** — `payload.data.key` accessed without null check
- **`ApiResponseCommand`** — `payload.request` and `payload.response` destructured without null checks
- **`StateValuesChangeCommand`** — insufficient type checking before `Object.keys()`
- **`BenchmarkReportCommand`** — `payload.steps` array accessed without validation, crashes on empty array
- **`SagaTaskCompleteCommand/Stateless`** — `payload.children.length` and `.map()` without array check

These were safe when the only payload source was the client SDK, but with the MCP server (#1598) there's now a second source of commands that may produce different shapes.

Locate AsyncStorageMutationCommand, ApiResponseCommand, StateValuesChangeCommand, BenchmarkReportCommand, and SagaTaskCompleteCommand/Stateless, then inspect each payload access described in the issue. Exercise the components with null, wrongly typed, and empty payload values; done means none of these shapes throws while valid payloads still work.

Written by the indexing model from the issue text.