refactor: hoist static values outside render loop

[TrevorBurnham]

This PR optimizes the CodeView component by moving static computations out of the per-line render loop.

Problem

The Children.map loop in InternalCodeView was computing values that don't change per-line:

1. clsx(styles["line-number"], styles.unselectable) - called for every line, always returns the same string
2. clsx(codeElement.props.className, wrapLines ? ...) - called for every line, only depends on wrapLines prop
3. Inline style objects { width: 1 } and { width: "auto" } - recreated on every render

For a code block with 500 lines, this means ~1000 unnecessary clsx calls per render.

Solution

• Hoist style objects to module-level constants (COL_STYLE_SHRINK, COL_STYLE_AUTO)
• Pre-compute line number className at module level (lineNumberClassName)
• Compute code line span className once before the loop (codeLineSpanClassName)

Testing

• All existing unit tests pass
• No changes to component behavior or API

Impact

• Reduced CPU work per render, especially for large code blocks
• Fewer object allocations (style objects are now singletons)
• More efficient garbage collection