feat(ie-css): implement CSS parser with rules, declarations, and value types #68

CSS parser consuming tokens from CssTokenizer:
- Stylesheet/Rule/Declaration types with PropertyId enum (~55 properties)
- parse_stylesheet() and parse_declarations() public API
- Qualified rule parsing: raw selector strings + declaration blocks
- Declaration parsing: property:value with !important detection
- Value types: CssValue (Length, Percentage, Number, Color, keywords,
  Auto, Inherit, Initial, None)
- Color parsing: #hex (3/4/6/8 digit), rgb()/rgba(), 16 named colors
- Length units: px, em, rem, %, vw, vh, vmin, vmax, ch, ex, pt
- Shorthand expansion: margin, padding, border, border-width/style/color
- Property inheritance classification, initial values
- At-rule skipping (@import, @media consumed but not processed)
- 14 parser tests + 26 tokenizer tests = 40 total

Author: thomasnemer

crates/ie-css/src/lib.rs

@@ -7,7 +7,9 @@ pub mod parser;
 pub mod selector;
 pub mod style;
 pub mod tokenizer;
+pub mod values;
 
-pub use parser::parse_stylesheet;
+pub use parser::{Declaration, Rule, Stylesheet, parse_declarations, parse_stylesheet};
 pub use style::ComputedStyle;
 pub use tokenizer::{CssToken, CssTokenizer};
+pub use values::{CssColor, CssValue, LengthUnit, PropertyId};