fix: Callback Error Handling

[monoxgas]

• Fix error handling for pipeline callbacks so they respect on_failed/catch settings

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Generated Summary

• Updated exception handling in the chat pipeline to assign errors directly to state.chat.error and mark state.chat.failed instead of raising immediately.
• Replaced separate task iteration with a combined zip of states and tasks (using strict=True) to ensure proper exception detection.
• Modified the asyncio.gather call to include return_exceptions=True, ensuring all tasks complete even when exceptions occur.
• Wrapped the map callback invocation in a try/except block, allowing exceptions to be caught and assigned to all relevant chats.
• Added new tests for both map and then callback exception handling to verify that RuntimeErrors are properly captured and propagated.

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