FOLLOW-UP: Duplicate style blocks per component instance

[adnaan]

Context

This follow-up task was identified during the review of PR #292.

Source PR: #292
Suggested by: @claude[bot]

Task Description

Each component template emits its own <style> block via _shared.tmpl:

<style>[data-dropdown]:not(.open) [data-dropdown-panel]{display:none}</style>

A page with three dropdowns produces three identical <style> blocks. Browsers handle this correctly but it is unnecessary HTML weight.

Fix options:

• Move these rules to the client library's stylesheet
• Use a template-level dedup mechanism (e.g., only emit if not already present)
• Document as a known trade-off

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This issue was automatically created from PR #292 review comments.