CRITICAL: core blocks emit raw 'style' STRING attrs → mass 'unexpected/invalid block content'; map to canonical block style attributes instead

[chubes4]

Root cause (pervasive)

The transformer emits raw inline CSS as a style STRING attribute on core blocks:

wp:paragraph {"className":"hero-eyebrow","style":"display:flex;align-items:center;..."}
wp:heading   {"style":"font-size:clamp(4rem,11vw,8rem);color:var(--rose-deep)"}
wp:group     {"style":"padding:clamp(...);background:radial-gradient(...)"}

Core blocks expect a structured style OBJECT (style.typography/style.color/style.spacing/style.border) + the layout attribute — NOT a raw CSS string. So the stored <p style="..."> doesn't match the block's save() output → the editor throws "This block contains unexpected or invalid content" for nearly every styled element (a wall of invalid blocks).

Detection vs fix

• DETECTED: the editor-validity gate (#537, validateBlock) flags these as gating findings on a live run — good, not silent.
• OPEN: the FIX — stop emitting raw style strings. Buttons were fixed for exactly this (Style fidelity: translate source CSS button styling onto native core/button attributes #241 → native style.color.*), but only buttons. Paragraph/heading/group/etc. still emit raw strings → the bulk of the invalid blocks.

Ask (generalize #241 to all blocks)

In the Style/ layer (StyleResolutionTrait, post-slice-5) + BlockFactory + the block-emission path, translate resolved CSS into canonical block attributes for ALL emitted blocks:

• typography → style.typography.{fontSize,fontWeight,lineHeight,letterSpacing,textTransform}
• color → style.color.{background,text} / backgroundColor/textColor
• spacing → style.spacing.{padding,margin,blockGap}
• border → style.border.*
• display:flex|grid → the block's layout attribute
• Anything not mappable to the block's supports → route via className + carried CSS (theme/companion plugin). NEVER a raw style string on a core block.
• Fold in hidden-state safety (CRITICAL: responsive/JS-hidden base states (display:none / visibility:hidden / opacity:0) frozen as static styles → permanently invisible content (nav, CTA) #259): don't freeze display:none/visibility:hidden/opacity:0 from responsive/JS-revealed base states.

Generic; no fixture strings. This is the central style-fidelity + block-validity fix — it eliminates the invalid-block wall AND makes imports actually look right. Closes #259 (hidden-state half) too.