fix: streamline page copying

[Cc-Cece]

What changed

• replace the single-option dropdown with a direct copy button
• fetch and copy each page's generated Markdown on one click
• show localized copying, success, and failure states
• add responsive styling and accessible live status feedback
• preserve English Markdown routes for English-page copying while keeping llms.txt Chinese-only

Why

The previous UI required opening a menu with only one action, provided no copy result feedback, and displayed untranslated labels.

Validation

• npm run typecheck
• npm run build
• verified Chinese and English button labels in generated HTML
• verified 50 Chinese and 50 English Markdown routes
• verified llms.txt still contains only 50 Chinese links
• verified Chinese/English pages and Markdown routes return HTTP 200 locally

The existing two broken-anchor build warnings are unchanged from main. The in-app browser was unavailable, so clipboard interaction was reviewed through the event handler and rendered output rather than an automated system-clipboard assertion.

[Cc-Cece]

Reviewed the complete remote diff and generated output. The custom button removes the redundant menu, localizes all states, reports success/failure accessibly, and cleans up its timer. Chinese-only llms indexing remains intact while localized Markdown routes support copying on both locales. TypeScript, production build, local route checks, and GitHub Actions pass. No blocking findings.