Address @ShenAC-SAC's BUG-007 review on #3131. `task_tool.py` actually
emits five terminal strings:
- `Task Succeeded. Result: …`
- `Task failed. …`
- `Task timed out. …`
- `Task cancelled by user.` ← previously matched none
- `Task polling timed out after N minutes …` ← previously matched none
The previous cut handled three; the last two fell through to the
"unknown content" branch and pushed the subtask card back to
`in_progress` even though the backend had already reached a terminal
state. Add explicit matches plus regression tests for both. The
`in_progress` fallback is now reserved for genuinely unrecognised
output (i.e. contract drift), as documented.
Refs: bytedance/deer-flow#3107 (BUG-007), bytedance/deer-flow#3131 review
The subtask card status machine matched only three English prefixes (`Task
Succeeded. Result:`, `Task failed.`, `Task timed out`). Anything else fell
through to `in_progress`, so a `task` tool error wrapped by
`ToolErrorHandlingMiddleware` (`Error: Tool 'task' failed ...`) left the card
spinning forever even after the run had ended.
Extract the prefix logic into `parseSubtaskResult` and recognise any leading
`Error:` token as a terminal failure. The extracted function is unit-tested
against the legacy prefixes plus the `AsyncCallbackManager` regression
captured in the upstream issue.
Refs: bytedance/deer-flow#3107 (BUG-007)
fancyboi999