feat(ui): refine history graph visuals and layout

Refines history panel visuals and layout, including min width handling.
Removes the old branch visibility select in favor of a dialog button.
It also adds a graph connector to show primary branches.
Adds branch chips, icons, and hover effects to commits for clarity.

- History panel visuals and min width updated to improve layout.
- Removed branch visibility select; added dialog to customize branches.
- Branch chips and graph connectors enhanced with icons and hover effects.

src/App.svelte

@@ -266,7 +266,7 @@
   const LEFT_STASH_PANEL_MAX_HEIGHT = 420;
   const LEFT_EXPLORER_PANEL_MIN_HEIGHT = 220;
   const HISTORY_ASIDE_DEFAULT_WIDTH = 620;
-  const HISTORY_ASIDE_MIN_WIDTH = 560;
+  const HISTORY_ASIDE_MIN_WIDTH = 420;
   const HISTORY_ASIDE_MAX_WIDTH = 920;
   const ERROR_AUTO_HIDE_MS = 6000;
   const COMMIT_HISTORY_PAGE_SIZE = 50;
@@ -4690,7 +4690,7 @@
       <section
         class="workspace"
         aria-label="Git workspace"
-        style="--left-sidebar-width: {leftSidebarWidth}px; --history-aside-width: {historyAsideWidth}px;"
+        style="--left-sidebar-width: {leftSidebarWidth}px; --history-aside-min-width: {HISTORY_ASIDE_MIN_WIDTH}px; --history-aside-width: {historyAsideWidth}px;"
       >
 
       <!-- Left sidebar: branches + explorer -->