[AI Bundle] Fix profiler serialization error with unconsumed streams

[camilleislasse]

Q	A
Bug fix?	yes
New feature?	no
Docs?	no
Issues	Fix #1121
License	MIT

Summary

Fix serialization error when using streaming models with the profiler.

When using a streaming agent, the DataCollector tries to serialize a Generator object which PHP doesn't allow. This happens when the stream hasn't been consumed before the profiler collects data.

Error:

Serialization of 'Generator' is not allowed

Fix:
Return null instead of the raw Generator when the stream hasn't been consumed. The actual content is only available after the stream is iterated, so there's nothing to display anyway.

• If stream is consumed → profiler shows the accumulated content (via resultCache)
• If stream is not consumed → profiler shows null instead of crashing

[camilleislasse]

need #1177 for phpstan

[OskarStark]

Rebase unlocked

[OskarStark]

Can you please rebase? Thanks

[OskarStark]

Thanks for fixing this bug @camilleislasse.