Fix frame duplicate naming, language input layout, and layer export formatting

[afffe18]

Motivation

• Ensure duplicated dataframes/frames get sequential numeric names (Dataframe N / Frame N) instead of propagating chained names like Frame 1 1.
• Make multi-select expand/collapse behavior reflect its button label (visible state must match Expand/Collapse).
• Improve JSON editor readability on light backgrounds and avoid conditional dark styling for that overlay.
• Emit a consistent, compact layer shape from the config export so regular layers contain only the primary fields while special trailing layers contain only alpha_points/alpha_areas.

Description

• Always call getNextTabName(..., 'Frame') / getNextTabName(..., 'Dataframe') when duplicating frames/dataframes so generated names follow numeric sequencing; adjusted duplicateFrame and duplicateDataframe in src/App.tsx.
• In MultiSelectInput reversed the height class logic so the DOM state matches the Expand/Collapse label.
• Replaced per-language toggle inputs with a stacked single-column layout for Title / Legend / Axis-label inputs showing language codes at the left, removing the now-unused expanded-per-language state variables in src/App.tsx.
• Made the JSON editor overlay use a white background + dark text and set the textarea caret to a dark color, and removed the conditional resolvedDarkMode usage for that area in src/App.tsx.
• Updated toExternalConfig in src/utils/configIo.ts to export layer objects conditionally: if a layer has no primary fields emit only alpha_points/alpha_areas, otherwise emit only the primary fields (name, whitelist_flag, whitelist, alpha, linewidth).

Testing

• Ran npm run build (which runs tsc -b && vite build); an initial build failed due to unused-state TypeScript errors, those were removed and the final build completed successfully.
• Verified the production build artifacts were produced by vite build as part of the npm run build step (build succeeded).

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Codex Task