fix(lint): match @font-face when a comment inside the block holds a brace

[leorivastech]

What

font_family_without_font_face (and system_font_will_alias) collect declared
@font-face families with @font-face\s*\{[^}]*\}. [^}]* stops at the first
}, so a CSS comment inside the block that contains a brace truncates the match
before font-family: is reached:

@font-face { /* weight 400 } regular */ font-family: 'Noto Sans SC'; src: url('...'); }

The family is never recorded as declared, and a later literal
font-family: 'Noto Sans SC' is then reported as used without an @font-face —
a blocking error since 0.6.109, where #1495 promoted this rule from warning to error.

Fix: strip CSS comments before scanning. In valid CSS the only source of a }
inside an @font-face block is a comment, so this closes the gap. It's the same
technique #1495 already applied to scene_layer_missing_visibility_kill ("strip
JS comments before pattern matching") and caption_transcript_parse_error
("balanced-bracket scanner replaces non-greedy regex") — just never applied to the
font rules.

Honest note on #1534

I believe this is the cause of #1534, but I want to be upfront: I could not
reproduce it with a clean @font-face, no matter how large/complex the
surrounding CSS was (tested 139-line blocks, 15 @keyframes, Fontsource-style
multi-line faces, comments that mention @font-face, two <style> blocks). The
only thing that reproduces the exact error is a brace inside the @font-face
block — realistically a comment. The reporter says the @font-face is byte-identical
between the passing and failing cases; if so, the failing file most likely has an
inline comment in the block that was dropped when minimizing the repro.

@Johnson-Jia — could you share the exact failing @font-face block (or the minimal
HTML) verbatim? If it carries a comment with a } inside, this fixes it; if not,
I'd like to track down the remaining mechanism. Marked Refs #1534 rather than
Fixes until that's confirmed.

Verification

• Added a regression test (comment-with-brace inside @font-face); confirmed it
  goes red on main and green with this change.
• packages/core: full lint suite 191/191, tsc --noEmit clean, and the
  pre-commit gate (oxlint + oxfmt + fallow audit) clean.