fix: recover shorthand CSS properties containing var() references

[LuLaValva]

I was playing with adding this to evo-web and ran into some issues.

When a CSS shorthand (e.g. border-radius) contains var() references, browsers list longhand names in style[i] but return empty strings for getPropertyValue() on each longhand. The previous rollup loop walked arbitrary dash segments instead of the CSS shorthand hierarchy, causing these properties to be silently dropped from snapshots.

Replace the rollup loop with a two-pass approach:

1. First pass iterates style[i] as before, tracking longhands with empty values in a Set instead of attempting dash-stripping
2. Second pass (only when empty longhands exist) parses style.cssText with a character-by-character parser that handles nested parentheses (e.g. var(--x, calc(100% - 20px))) to recover shorthand declarations

Also strips !important suffixes from cssText values since priority is handled separately via getPropertyPriority().