[chubes4]

Fixes #3422.

Root cause

A source rule such as .nav > li > a span { font:10px; display:block } is written for the subtitle span inside a link. Core navigation wraps each link's whole text in its own <span class="wp-block-navigation-item__label">, so once a is projected, the author span also matched that wrapper. The entire label then rendered at 10px as a block. The projection happens on two paths, and both lacked the guard:

• the HtmlToBlocks author-stylesheet projector (type-span rewrite);
• the site-compile WordPressCompatCss navigation mapping (a → .wp-block-navigation-item__content), which real imports use.

Fix

Both paths now emit span:not(:where(.wp-block-navigation-item__label)). This adds no specificity, real source spans stay matched, and only the engine-owned wrapper is excluded.

Evidence

• tests/unit/navigation-label-wrapper-author-span.php covers the HtmlTransformer cascade (including a dormant rule) and the ArtifactCompiler site compile. Both fail on trunk.
• composer test:unit is green.
• Paired build: studio create --from <reduced site> --static-site-importer-path <SSI dev zip with this branch>, Chromium at 1200px:

	source	trunk (v0.44.151)	this PR
label font	18px / 700	10px / 400	18px / 700
subtitle font	10px	10px	10px
item box	94×69	92×56	94×69

The first commit (the projector path) passed its own unit test, but the real import was unchanged. Measuring in the browser located the second path; this is why the test now also covers the site compile.

AI disclosure: the fix was drafted by a Homeboy cook (Pi coding agent, roadie/cook-heavy: gpt-6.1-sol). Homeboy marked the green candidate candidate_recoverable (Extra-Chill/homeboy#16418), so it was promoted to this branch with homeboy agent-task promote. Claude (Anthropic), running in Pi, then reviewed it, re-ran verification and paired-build evidence, and pushed it.