rgitui v0.1.8

Added

• Custom theme editor (Ctrl+Shift+T / Alt+9): live color-picker UI for all
  theme fields with hex input and swatch preview. Edited themes are saved as
  JSON files to ~/.config/rgitui/themes/ and reloaded on next launch.
• JSON theme serialization: themes can be exported and re-imported as JSON.
  Built-in themes ship as embedded JSON; user themes are loaded from the config
  directory at startup.
• Branch from stash: a Branch button on each stash panel row lets you create
  a branch from any stash entry directly, without going through the command
  palette.

Fixed

• Theme editor black-on-save regression: saving a theme no longer
  momentarily resets all colors to black; the editable state is properly
  resynced after save.
• Theme editor startup popup: opening the editor no longer flashes an empty
  or stale state on first render.
• Invalid hex fallback in theme editor: typing a partial hex value no longer
  silently snaps the swatch to black; the swatch holds the field's current theme
  color until a valid hex is entered.
• Graph lane-0 gap: lane 0 is now drawn continuously from the first
  side-branch curve-in to main_tip, preventing gaps when the newest commits
  are on side branches.
• is_merged_into_main correctness: merge detection now uses merge_base
  instead of graph_descendant_of, fixing false positives on non-linear
  histories.
• Search output parser: malformed git grep output no longer silently drops
  results; a simple-split fallback preserves partial matches.
• Windows UNC paths (WSL2): repository paths beginning with
  \\server\share\… are rewritten to //server/share/… for libgit2
  compatibility. Extended-length (\\?\) and device (\\.\) prefixes are left
  unchanged.