fix(desktop): refine Author document tabs

[agentfleets]

Summary

• keep Author filenames readable with stable tab widths and dedicated ellipsis
• add overflow controls, automatic active-tab reveal, and Arrow/Home/End navigation
• refine active, dirty, draft, agent-edit, and close states in both themes
• localize the new overflow-control labels in English and Chinese

Verification

• cd desktop && npm run build
• cd desktop && node --test src/state/*.test.ts src/ui/*.test.ts src/ssh/*.test.ts src/terminal/*.test.ts (794 pass)
• bash scripts/lint-desktop-tokens.sh
• visual QA at 1228x768 with 12 open documents in dark and light themes; no browser console errors

[agentfleets]

Closing as superseded by #540, which merged the Author tab-strip behavior together with the broader workbench visual polish.