feat(cssom): expose the selectors text at style rule

[yorkie]

This pull request adds support for retrieving and exposing the raw CSS selector text for style rules in the bindings between Rust and C++. This enhancement allows consumers of the C++ API to access the original selector string as authored, which can be useful for debugging, serialization, or advanced CSSOM operations. The changes include updates to the Rust data model, FFI layer, and C++ bindings.

[Copilot]

Pull Request Overview

This pull request adds support for exposing the raw CSS selector text in style rules across the Rust-C++ bindings layer. The enhancement enables C++ API consumers to access the original selector string as authored in CSS, which is valuable for debugging, serialization, and advanced CSSOM operations.

• Adds a new selectorsText() method to the C++ StyleRule class that returns the raw selector string
• Implements the underlying Rust functionality to convert selectors to CSS text using the ToCss trait
• Updates the FFI layer to bridge the selector text from Rust to C++

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/client/cssom/rules/css_style_rule.hpp	Adds TODO comment about future C++ parser migration
crates/jsbindings/css_parser.rs	Adds FFI function to expose selector text from Rust
crates/jsbindings/css/stylesheets/style_rule.rs	Implements selector-to-text conversion using ToCss trait
crates/jsbindings/bindings.css.hpp	Adds selectorsText member and accessor method to C++ StyleRule class