FEATURE: forum researcher persona for deep research

[SamSaffron]

This commit introduces a new Forum Researcher persona specialized in deep forum content analysis along with comprehensive improvements to our AI infrastructure.

Key additions:

• New Forum Researcher persona with advanced filtering and analysis capabilities
• Robust filtering system supporting tags, categories, dates, users, and keywords
• LLM formatter to efficiently process and chunk research results

Infrastructure improvements:

• Implemented CancelManager class to centrally manage AI completion cancellations
• Replaced callback-based cancellation with a more robust pattern
• Added systematic cancellation monitoring with callbacks

Other improvements:

• Added configurable default_enabled flag to control which personas are enabled by default
• Updated translation strings for the new researcher functionality
• Added comprehensive specs for the new components

This change makes our AI platform more stable while adding powerful research capabilities that can analyze forum trends and surface relevant content.

[romanrizzi]

Changes look good. The CancelManager is a very nice improvement.

Something I have mixed feelings about is where the object is istantiated. I'd prefer it to bubble from the bottom like before this change, but we'd need a better completion response abstraction to properly support that, so not pushing for that right now.

[SamSaffron]

I actually regret bubbling it from the block cause it forces you to keep repeating it which is a bit confusing. Plus if you are waiting a minute for the first few bytes from the LLM you need to bubble it right away which means you say "here is no text, but in case you need to cancel you can use this"

having it passed in gives us so much more consistency (now that endpoint/base and open ai image generation both share the pattern)