Migrate task progress, events, and cancellation

[quinCode]

Migrate task progress, events, and cancellation

Parent

#2

What to build

Migrate task progress, progress events, sample status, and cancellation into the new architecture. Core progress events should be parsed only by CoreGateway or backend services and normalized before reaching React.

This slice should keep the existing live run monitoring behavior while removing frontend dependency on raw LLMSTP_EVENT lines.

Acceptance criteria

• UI backend exposes typed task status, task events, and cancel routes.
• CoreGateway or backend services parse progress events and normalize run, sample, error, and completion states.
• React progress feature displays run progress, sample status, current sample, errors, and completion state from UI application model data.
• Cancellation works for running tasks and returns a normalized task state.
• Fake core CLI tests cover event ordering, unknown event types, malformed event lines, run errors, and cancellation behavior.
• Frontend feature tests cover running, completed, error, and cancelled states.
• React code does not parse raw stdout or LLMSTP_EVENT prefixes.

Blocked by

• Migrate run creation and validation through CoreGateway #8