* feat: add task-level retry with exponential backoff
Add `maxRetries`, `retryDelayMs`, and `retryBackoff` to task config.
When a task fails and retries remain, the orchestrator waits with
exponential backoff and re-runs the task with a fresh agent conversation.
A `task_retry` event is emitted via `onProgress` for observability.
Cascade failure only occurs after all retries are exhausted.
Closes#30
* fix: address review — extract executeWithRetry, add delay cap, fix tests
- Extract `executeWithRetry()` as a testable exported function
- Add `computeRetryDelay()` with 30s max cap (prevents runaway backoff)
- Remove retry fields from `ParsedTaskSpec` (dead code for runTeam path)
- Deduplicate retry event emission (single code path for both error types)
- Injectable delay function for test determinism
- Rewrite tests to call the real `executeWithRetry`, not a copy
- 15 tests covering: success, retry+success, retry+failure, backoff
calculation, delay cap, delay function injection, no-retry default
* fix: clamp negative maxRetries/retryBackoff to safe values
- maxRetries clamped to >= 0 (negative values treated as no retry)
- retryBackoff clamped to >= 1 (prevents zero/negative delay oscillation)
- retryDelayMs clamped to >= 0
- Add tests for negative maxRetries and negative backoff
Addresses Codex review P1 on #37
* fix: accumulate token usage across retry attempts
Previously only the final attempt's tokenUsage was returned, causing
under-reporting of actual model consumption when retries occurred.
Now all attempts' token counts are summed in the returned result.
Addresses Codex review P2 (token usage) on #37
JackChen