Langroid

fix: chat_context_length lookup, web_search

- gemini models - recognize both "bare" names like `gemini-2.0-flash` as well as those like `gemini/gemini-2.0-flash` when looking up model
info
- whenever `OpenAIGPTConfig.chat_context_length` is explicitly given, use it
- `web_search.py` - handle edge cases like long docs etc

feat: allow settings in OpenAIEmbeddingsConfig to be set via `OPENAI_...` env vars in `.env` file or system env.

E.g. if `OPENAI_API_BASE` is set in the env, it will be picked up in `OpenAIEmbeddingsConfig`, similar to how it's
used in `OpenAIGPTConfig`.

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feat(minor): Set `ParsingConfig.page_number_offset` = x, if "displayed" page number 1 starts at physical page 1 + x

This ensures that page numbers in source citations match the "displayed" page numbers in a document.

feat(minor): options to control citation detail, agent response rendering.

- `Agent.render_agent_response` method to display agent response, controled by option `hide_agent_response`
- `AgentConfig.hide_agent_response` - set to `True` to hide agent response (useful where tool-handlers send large response to LLM, but
we don't want to clutter display with it)
- `ChatAgentConfig.full_citations` - whether to show citations with content or not. If `False`, only show main reference in footnote, not the
whole content.