fix(lint): flag hidden-style opacity guards

[miguel-heygen]

What

lint and check now reject broad CSS guards that turn renderer-owned visibility: hidden into opacity: 0. This prevents successfully extracted video frames from becoming transparent while keeping guards explicitly scoped to sub-composition hosts valid.

Why

The renderer hides each native video before it copies the video's computed opacity to the visible replacement image. A broad [style*="visibility: hidden"] opacity rule observes that runtime mutation, sets the native opacity to zero, and causes the copied frame to remain transparent for every rendered frame.

How

• Reuse the existing parsed CSS selector pass and resolve nested selectors before evaluating them.
• Inspect the selected compound, so an ancestor scope does not make an arbitrary media target safe.
• Allow the guard only when that selected compound is explicitly constrained to data-composition-src or data-composition-file.
• Preserve engine host filtering and authored media-opacity semantics.

Test plan

• RED/GREEN coverage for broad, media-targeted, and root-stylesheet/nested-video cases.
• Safe host-scoped and non-opacity controls remain accepted.
• Full lint package: 553 tests passed.
• Lint package typecheck, oxlint, formatting, and diff checks passed.
• Documentation updated (not applicable).

[miga-heygen]

Hidden-style opacity guard lint rule with proper CSS selector parsing. Correctly exempts sub-composition host scoping and non-opacity declarations. — Miga