Goal mode aborts instead of continuing after a Task reaches max_turns

[zzzbitz]

Problem

In Goal mode, if the current Task reaches max_turns, the Goal immediately ends as aborted and no new Task is started, even when the Goal has no token budget limit.

Current behavior:

Task 1 reaches max_turns
→ final message has stop_reason: failed
→ goal_finished(outcome: aborted)

This prevents Goal mode from helping the long-running tasks that most need continuation.

Expected behavior

Keep max_turns as the limit for one Task, but treat reaching it as a round boundary:

Task 1 reaches max_turns
→ preserve workspace and progress
→ start Task 2 for the same Goal

The Goal can still be bounded by its token budget, maxRounds, user aborts, and no-progress protection.

Relevant code

packages/core/src/goal/goal-loop.ts currently treats a max-turn cutoff as terminal via roundFailed and returns goal_finished("aborted").