feat: simplify styles, give querychat components classes

[gadenbuie]

A few style-level changes to align Python and R packages and improve styles:

• Use same styles.css file in both packages
• Add .querychat to the chat_ui() component used by querychat
• Add .querychat-sidebar to the sidebar() created by querychat_sidebar()
• Use new client argument in Python examples
• Adjust position of sidebar collapse toggle in querychat_sidebar() to stay out of the way of tool cards in the sidebar.

[Copilot]

Pull Request Overview

This PR standardizes styles between Python and R packages and improves component identification by adding CSS classes to querychat components.

• Unified styles.css files between Python and R packages for consistent styling
• Added .querychat and .querychat-sidebar CSS classes to components for better customization
• Updated Python examples to use the new client argument instead of deprecated create_chat_callback

Reviewed Changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg-r/man/querychat_ui.Rd	Updated documentation formatting and cross-references
pkg-r/man/querychat_init.Rd	Improved documentation formatting and line wrapping
pkg-r/inst/htmldep/styles.css	Simplified CSS to match Python package and added sidebar collapse positioning
pkg-r/R/querychat_app.R	Added bslib-page-dashboard class and cleaned up function call
pkg-r/R/querychat.R	Added CSS classes to components and improved documentation
pkg-r/NEWS.md	Added changelog entry for new CSS classes
pkg-py/src/querychat/static/css/styles.css	Unified with R package styles
pkg-py/src/querychat/querychat.py	Added querychat CSS classes to UI components
pkg-py/examples/*.py	Updated to use client instead of create_chat_callback
pkg-py/CHANGELOG.md	Added changelog entry for new CSS classes

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