Fix #4395: CSS minifier drops parentheses around nested or in @media rules

[cobyfrombrooklyn-bot]

When minifying @media only screen and ((min-width: 10px) or (min-height: 10px)), the outer parentheses around the or condition were dropped, producing invalid CSS:

/* Input */
@media only screen and ((min-width: 10px) or (min-height: 10px)) { color: blue }

/* Before (invalid) */
@media only screen and (min-width:10px)or (min-height:10px){color:blue}

/* After (correct) */
@media only screen and ((min-width:10px)or (min-height:10px)){color:blue}

The CSS spec requires or clauses to be parenthesized when used after a media type with and. Without the outer parens, browsers ignore the entire media query.

Fix

In css_printer.go, when printing MQType.AndOrNull, pass mqNeedsParens if the inner query is an MQBinary with Or operator.

Test

Added 3 test cases in css_printer_test.go for TestAtMedia:

• Minified: only screen and ((min-width: 10px) or (min-height: 10px)) preserves outer parens
• Minified: screen and ((a) or (b)) preserves outer parens
• Pretty-printed: same input preserves structure

All tests fail without the fix, pass with it. Full test suite passes on macOS ARM (Apple Silicon).

Fixes #4395