isLoopFinished

Consolidated check: would the loop terminate after this state?

Mirrors v6's isLoopFinished helper — useful when callers want to pre-check whether a [StopCondition] would fire without driving the loop manually.

Returns true if any of:

• The supplied stopWhen reports shouldStop = true

• The last step's finish reason is Stop and no tools were called

• The last step's finish reason is ToolApprovalRequested (loop pauses for host to resume)

• The last step's finish reason is Length / ContentFilter (provider terminated, can't continue)