release: publish v2.0.20 selection and sidebar refinements

Complete zero-width sidebar collapse with synchronized bidirectional motion, add package-row selection and guarded double-click disclosure, render continuous selection edges across nested package boundaries, expand regression coverage, and update the public English changelog and package metadata for v2.0.20.

src/renderer/shell/shell.css

@@ -404,6 +404,7 @@
   min-height: 0;
   grid-template-columns: minmax(0, 1fr);
   gap: 8px;
+  transition: grid-template-columns 520ms cubic-bezier(0.22, 0.76, 0.22, 1);
 }
 
 .md-shell.has-sidebar .md-shell-workspace {
@@ -411,10 +412,10 @@
 }
 
 .md-shell.has-collapsed-sidebar .md-shell-workspace {
-  grid-template-columns: 56px minmax(0, 1fr);
+  grid-template-columns: 0 minmax(0, 1fr);
 }
 
-.md-shell-sidebar,
+.md-shell-sidebar-panel,
 .md-shell-main {
   position: relative;
   min-width: 0;
@@ -425,8 +426,24 @@
 }
 
 .md-shell-sidebar {
+  position: relative;
+  z-index: 4;
+  min-width: 0;
+  min-height: 0;
+}
+
+.md-shell-sidebar-panel {
   display: flex;
+  width: 270px;
+  height: 100%;
   flex-direction: column;
+  opacity: 1;
+  transform: translate3d(0, 0, 0);
+  visibility: visible;
+  transition:
+    opacity 260ms ease,
+    transform 520ms cubic-bezier(0.22, 0.76, 0.22, 1),
+    visibility 0s linear 0s;
 }
 
 .md-shell-sidebar-scroll {
@@ -465,16 +482,12 @@
   line-height: 16px;
 }
 
-.md-shell-sidebar.is-collapsed :where(.md-shell-sidebar-scroll, .md-shell-sidebar-status) {
-  overflow: hidden;
+.md-shell-sidebar.is-collapsed .md-shell-sidebar-panel {
   visibility: hidden;
   opacity: 0;
-  transform: translateX(-8px);
-}
-
-.md-shell-sidebar-scroll,
-.md-shell-sidebar-status {
-  transition: opacity 160ms ease, transform 160ms ease;
+  transform: translate3d(calc(-100% - 8px), 0, 0);
+  pointer-events: none;
+  transition-delay: 0s, 0s, 520ms;
 }
 
 .md-shell-sidebar-toggle {
@@ -507,6 +520,7 @@
 }
 
 .md-shell-sidebar:hover .md-shell-sidebar-toggle,
+.md-shell-sidebar.is-collapsed .md-shell-sidebar-toggle,
 .md-shell-sidebar-toggle:focus-visible {
   opacity: 1;
 }
@@ -907,6 +921,14 @@
     transition-duration: 0.01ms !important;
   }
 
+  .md-shell-workspace {
+    transition-duration: 520ms !important;
+  }
+
+  .md-shell-sidebar-panel {
+    transition-duration: 260ms, 520ms, 0s !important;
+  }
+
   .md-shell-navigation::before {
     transition-duration: 420ms, 420ms, 420ms, 120ms !important;
   }