Improve Viewer and ring editing workflow

[happykhan]

What changed

• Adds the top-level read-only Viewer for local files and public GitHub session URLs.
• Shows result statistics and saved BLAST-output downloads in Viewer.
• Adds a draggable, resizable, minimisable and dockable Ring Configuration panel.
• Keeps annotation editing above floating panels and fixes the sticky table header.
• Improves ring-card layout, collapse controls, file selection, bug reporting and user-facing logs.
• Removes automatic reference CDS annotations and the temporary preview-store flow.
• Updates BRIGX documentation and regression coverage.

Why

This brings the local UI work into one coherent production workflow: users can configure rings while watching the plot, share saved results through Viewer, inspect statistics, and download embedded alignment results without rerunning BLAST.

Validation

• npm run verify
• Lint, architecture, licence and security checks passed.
• 176 unit tests passed.
• Production build passed.
• 23 production-browser tests passed.
• Vite development-mode WASM alignment test passed.

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