GitCat v1.3.0

This release focuses on matching GitKraken's commit graph exactly: lane placement,
branch colors, edge paint order, and page-independent layout. It also fixes several
stash operations that were resolved by an unstable index.

Added

• Show the popped stash's message as the WIP row title until the next mutation.
• Automated GitKraken graph conformance suite, with recorded oracles for the
  merge ladder, stash-on-ladder, overflow palette blocks, SVG crossing paint order,
  and multi-lane convergence pagination.

Fixed

• Lane placement: a tip now reuses the lowest interior lane emptied by a
  convergence instead of always opening to the right of the rightmost active lane.
• Merge lanes: a new merge-parent line opens beside its own merge rather than
  past unrelated routes that happen to be open further right.
• Merge ladders: repeated merges of the same trunk into one branch now fan into
  their own lanes and draw a ladder instead of collapsing into a straight column;
  a ladder rung keeps reserving the lane it steps out of.
• Pagination: merge-line lane reservations now survive a history page boundary,
  so paging through history in any number of batches produces the same lanes and
  edges as a single-batch layout.
• Colors: branch colors follow the physical lane (color = lane % 10), matching
  GitKraken; built-in theme graph palettes now define all 10 canonical lane slots.
• Paint order: at every SVG crossing the physically backmost route is painted
  on top.
• Stash: apply, pop, and drop now resolve by stable outer oid instead of index,
  and the delete confirmation names the stash by its message.