[Bug]: GoalPipeline ignores max_retries for invalid structured outputs

[helloJamest]

Prerequisites

• I have searched the existing issues and discussions, and this is not a duplicate.
• This is a bug, not a usage question.

Background / Description

GoalPipeline.__init__ documents max_retries as the maximum number of retries for the executor and verifier to generate valid structured outputs, and stores it as self.max_retries. However, neither structured-output retry loop reads that value.

When either agent repeatedly completes without structured_output, GoalPipeline.reply_stream() invokes it indefinitely. The verifier has another unbounded path when its stream ends without a completed final message: if final_msg is None: continue.

This is separate from max_iters: max_iters limits executor-verifier goal attempts after an explicit fail verdict, while malformed or missing structured output is retried inside a single goal attempt.

Expected behavior

max_retries should bound malformed/missing structured-output retries independently for the executor and verifier. Following the existing AgentScope retry convention, max_retries=1 should allow the initial call plus one retry. Once exhausted, the pipeline should raise a clear error instead of silently appearing to finish.

HITL and external-execution events should continue to park the pipeline without consuming the malformed-output retry budget.

Actual behavior

With max_retries=1, both executor and verifier can be called more than two times and continue indefinitely if they never produce structured output.

Error Messages

No exception is raised by GoalPipeline. A guarded reproducer stopped each loop after the fifth call:
executor: guard stopped executor; calls=5; configured_retries=1
verifier: guard stopped verifier; calls=5; configured_retries=1

Steps to Reproduce

The existing StubAgent and _no_output helpers in tests/pipeline_goal_test.py can reproduce the behavior:

executor = StubAgent("executor", [[_no_output("executor")]])
verifier = StubAgent("verifier", [[_verdict("pass")]])
pipe = GoalPipeline(executor, verifier, max_retries=1)

await self._run(pipe, self.query)  # never returns

The same occurs on the verifier path:

executor = StubAgent("executor", [[_report()]])
verifier = StubAgent("verifier", [[_no_output("verifier")]])
pipe = GoalPipeline(executor, verifier, max_retries=1)

await self._run(pipe, self.query)  # never returns

Proposed fix

• Enforce max_retries + 1 total attempts separately in the executor and verifier structured-output loops.
• Treat a verifier stream with no completed final message as an invalid attempt too.
• Preserve existing HITL and max_iters behavior.
• Add regression tests for executor exhaustion, verifier exhaustion, and success on the last allowed attempt.

I would be happy to prepare a focused PR for this.

Environment

• AgentScope Version: main at 10eaaac269101e25ad9f808353c45e305c6d7231
• Python Version: 3.11
• OS: Windows 11