Preserve collapsed geometry for static select controls

## Problem

Static non-runtime `` controls are converted into visible `core/list` option inventories. This destroys control geometry and displays every option.

Canonical fixture `20-switchback-woocommerce-extra-hard` contains four styled collapsed selects in its guided selector. The generated candidate emits `core/group.form-select` with a duplicate label paragraph and a visible `core/list` for each control.

Measured at 1280px:

- source page: `1280 x 6761`
- candidate: `1280 x 7245`
- candidate `` expansion: `435.66px`
- footer shift/candidate tail: `484px`
- aligned visual mismatch after prior hero repair: `9.0845%`

The immutable fixture must remain unchanged.

## Owner

`php-transformer/src/HtmlToBlocks/HtmlTransformer.php`: `readableSelectBlockFromElement()` emits the expanded group/list shape. Existing contract coverage currently requires static selects to become readable lists.

## Acceptance

- A static select with authored layout/style remains a compact collapsed control, not an always-visible option list.
- Preserve class, id, name, selected/placeholder state, label association, and applicable authored CSS.
- Keep runtime-targeted select island behavior unchanged.
- Use a generic editable/native control representation with no fixture-specific selectors/classes.
- Fixture 20's four controls restore source main geometry while editor validity and zero-fallback contracts remain green.
- Replace the current visible-list contract with positive static-control and negative runtime-targeted coverage.

## Related

#220 is a forms parity umbrella and #718 covers pseudo-form ownership; neither owns this static control expansion.

## AI assistance

OpenAI gpt-5.6-terra via OpenCode and a general OpenCode subagent compared immutable source/candidate DOM geometry and isolated the static select conversion contract. Chris Huber directed the investigation and remains responsible for the issue and resulting change.

Start in php-transformer/src/HtmlToBlocks/HtmlTransformer.php at readableSelectBlockFromElement(), then inspect the immutable 20-switchback-woocommerce-extra-hard fixture and the existing static-select readable-list contract. Confirm the four styled controls retain compact geometry and authored state while runtime-targeted selects keep their island behavior; editor-validity and zero-fallback contracts should remain green.

Written by the indexing model from the issue text.