feat(ui): labelled compact Ribbon that narrows without disappearing

[Limdongcheng]

Summary

The compact density kept only the icon of every icon-bearing command, which turned each shared or abstract glyph into a guessing game and left the buttons without accessible text; below 760 px the whole command area vanished, stranding macOS users (no in-app menu bar) with the palette as the only escape.

• Compact buttons pair the glyph with their short label, sized by measurement; narrow windows pay their identification cost in the More menu instead of on unlabelled icons.
• Width no longer collapses the command area: narrow windows stay on the compact row and overflow absorbs the groups, degrading in the extreme to the More menu alone. Collapsed remains a deliberate, user-only state; the auto-collapse control and message are gone.
• Overflow admission lets equal-priority peers keep taking space when an oversized group overflows, so the ten-tile Processing group no longer dams Transform and Recipes behind it. A hidden group is still never outranked by a shown one; tests pin both properties.
• The quick tour's responsive description (EN and zh-CN) matches the new behaviour.

Validation

• cargo pr-check passes (fmt, file size, dependency policy, both frontends, clippy with denied warnings, tests).
• Unit tests: density never returns Collapsed for width alone, the overflow prefix invariant, and the equal-priority peer case.
• npm run build in docs/ passes.

UI display logic

• New or changed actions go through the command catalog (CommandId +
  describe) and are searchable in the command palette. (No actions added.)
• Hiding happens only at Ribbon-group level (dataset kind or width
  budget); transient states disable with a disabled_reason that says how
  to unblock.
• No layout changes from background events; panels are never auto-closed.
  (Width no longer hides the command area at all.)
• New panels or empty regions show an empty state with a next step. (None
  added.)
• Docs updated in docs/ (English and zh-CN) for user-visible behavior.

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