Langroid

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.

build: remove `docling`, `tavily` from core dependencies (they are optional, installable via extras)

feat: pdf parsing with Marker - see [docs](https://langroid.github.io/langroid/notes/marker-pdf)

Thank you, abab-dev !

fix: remove double-indented "cached" line in agent outputs.

feat: late imports to reduce load time of top level modules (langroid, etc)

fix: fix incorrect strict-recovery in `get_tool_messages(str)`

Extends the fix in 758 to string-typed calls to get_tool_messages for ChatAgents
by ensuring that the recovery flag is sent only when one of the following is true:
- the most recent message in the history was produced by the LLM, or
- the argument is a ChatDocument sent by the LLM.

Resolves 753

Thanks nilspalumbo!