Problem:
- Clicking Terminate during streaming caused the entire chat view to blink
- Task would close, user pushed to home, then back into the task
- Cancel → Resume flow would grey the Resume button but not restart the loop
- Input would become disabled and messages couldn't be sent

Root causes:
1. Hard abort (abandoned=true) was disposing the task instance immediately
2. Provider was rehydrating a new task instance from disk after abort
3. Abort flags stayed set (abort=true) preventing loop resumption
4. No deterministic spinner stopping on cancellation
5. Streaming state wasn't reset on resume

Solution:
- Soft-interrupt: Cancel now uses abortTask(false) to keep instance alive
- No rehydration: Provider skips task recreation for user_cancelled aborts
- Resume pipeline: Added presentResumableAsk() for in-place resume flow
- Abort state reset: Clear abort flags and streaming state before resuming
- Spinner determinism: Inject cancelReason into last api_req_started
- Transactional UI: Pause state updates during checkpoint operations

Changes:
- Task.presentResumableAsk(): New method for soft-interrupt resume
- Task.resumeTaskFromHistory(): Reset abort/streaming state after user confirms
- Task.abortTask(): Distinguish soft (keep alive) vs hard abort (dispose)
- ClineProvider.cancelTask(): Soft abort + schedule presentResumableAsk()
- ClineProvider.onTaskAborted: Skip rehydration for user_cancelled
- ChatView: Handle cancelReason for deterministic streaming state

Tests:
- Task.presentResumableAsk.abort-reset.spec.ts: Verify abort flag reset
- ClineProvider.cancelTask.present-ask.spec.ts: Verify soft-interrupt flow
- Task.spec.ts: Updated abort semantics (soft vs hard)

Result:
- No UI flicker or navigation on Cancel
- Resume button successfully restarts the agent loop
- Input remains enabled throughout cancel/resume cycle
- Spinner stops deterministically on cancellation
- Task history stable, no duplicate entries

The logic was inverted - when cost is defined in api_req_started, it means the API request has finished (streaming is complete), so should return false, not true.

When api_req_started exists without cost or cancelReason fields, the API request is still in progress and should be treated as streaming. Only return false when cost (completed) or cancelReason (cancelled) are present.

…SON parsing

- Extract duplicated abort/streaming state reset logic into private helper method resetAbortAndStreamingState()
- Update resumeTaskFromHistory() and presentResumableAsk() to use the helper method
- Replace unsafe JSON.parse() with safeJsonParse() in ClineProvider.ts for better error handling

Addresses review feedback from @mrubens on PR #8986