feat(ui): unify panel visibility controls

[Limdongcheng]

Summary

• Use matching panel visibility icons for the Ribbon and sidebar toggles.
• Apply the same collapse and close button styling to CRAFT, curve fitting, processing, region analysis, and statistics task cards.
• Update the English and Simplified Chinese Ribbon and UI overview documentation.

Validation

• cargo pr-check on macOS arm64.
• npm run build in docs/.
• git diff --check.
• Screenshot harness: expanded and collapsed task cards and Ribbon controls in light and dark themes, including a narrow window.

UI display logic

• Existing toggle, collapse, and close actions retained.
• Ribbon group visibility and disabled states retained.
• Panel visibility changes only through explicit controls.
• English and Simplified Chinese documentation updated.