Diple 0.3.0

Added

• Read-only History workspace on 3, with a bounded all-ref commit graph, decorations, authors,
  relative dates, keyboard navigation, mouse navigation, and refresh-in-place.

Changed

• Refined the interface with neutral pane borders, background-free header and footer chrome, and
  clearer file-tree hierarchy.
• Replaced the muddy neutral active-row fill with a clean, theme-aware cool-blue highlight while
  keeping text selection visually distinct.
• Compact tab labels automatically on narrow terminals so scope and commit identity remain visible.

Removed

• Pull-request and merge-request workspace from the public tab bar, keymap, and footer hints.