feat: implement math style and size switches in LaTeX parser

- Added functions to parse LaTeX commands for math styles (`\displaystyle`, `\textstyle`, `\scriptstyle`, `\scriptscriptstyle`) and font sizes (`\tiny`, `\scriptsize`, `\footnotesize`, `\small`, `\normalsize`, `\large`, `\Large`, `\LARGE`, `\huge`, `\Huge`).
- Updated the LaTeX definitions to utilize the new parsing functions.
- Enhanced the test suite to cover new functionality for math style and size switches, ensuring correct parsing and serialization.
- Adjusted existing tests to reflect changes in output structure for annotated expressions.

Author: arnog

CHANGELOG.md

@@ -1,3 +1,15 @@
+### [Unreleased]
+
+#### Fixed
+
+- **LaTeX parsing: style, size, and color switch commands** —
+  `\displaystyle`, `\textstyle`, `\scriptstyle`, `\scriptscriptstyle`,
+  `\tiny`..`\Huge` (10 size commands), and `\color{...}` were silently
+  discarded during parsing. They now produce `Annotated` expressions that
+  preserve the styling information and round-trip correctly through
+  serialization. Added `\scriptstyle` / `\scriptscriptstyle` serialization
+  support (previously only `\displaystyle` and `\textstyle` were handled).
+
 ### 0.55.5 _2026-03-06_
 
 #### Fixed