Feat: Add responsive workspace shell

Frontend/src/components/shell/LeftRail/LeftRail.module.scss

@@ -1,6 +1,5 @@
 .rail {
   --rail-workspace-size: var(--control-size-lg);
-  --rail-action-size: var(--control-size-md);
   position: relative;
   z-index: 3;
   flex: 1;
@@ -9,21 +8,19 @@
   flex-direction: column;
   align-items: center;
   gap: var(--space-3);
-  padding: var(--space-3) var(--space-2) calc(var(--space-3) + var(--rail-dock-clearance, 8rem));
+  padding: var(--space-3) var(--space-2) calc(var(--space-3) + var(--rail-dock-clearance, var(--shell-dock-clearance)));
   overflow: visible;
 }
 
 .railCollapsed {
   --rail-workspace-size: calc(var(--control-size-md) + 0.1rem);
-  --rail-action-size: calc(var(--control-size-md) + 0.1rem);
   justify-content: flex-start;
   gap: 0;
   padding-top: var(--space-4);
   padding-inline: var(--space-1);
 }
 
-.topCluster,
-.bottomCluster {
+.topCluster {
   width: 100%;
   display: flex;
   flex-direction: column;
@@ -31,11 +28,6 @@
   gap: var(--space-2);
 }
 
-.bottomCluster {
-  margin-top: auto;
-  margin-bottom: var(--rail-bottom-offset, 0rem);
-}
-
 .topCluster {
   gap: var(--space-3);
 }
@@ -44,8 +36,7 @@
   gap: var(--space-3);
 }
 
-.railCollapsed .topCluster,
-.railCollapsed .bottomCluster {
+.railCollapsed .topCluster {
   align-items: center;
 }
 
@@ -191,20 +182,3 @@
   border-radius: var(--radius-md);
   box-shadow: none;
 }
-
-.addButton {
-  width: var(--rail-action-size);
-  height: var(--rail-action-size);
-  display: inline-flex;
-  align-items: center;
-  justify-content: center;
-  border: 1px dashed var(--color-border-strong);
-  border-radius: var(--radius-pill);
-  background: transparent;
-  color: var(--color-text-muted);
-
-  &:hover {
-    background: var(--color-surface-hover);
-    color: var(--color-text);
-  }
-}

Frontend/src/components/shell/LeftRail/LeftRail.tsx

@@ -1,7 +1,6 @@
 // Path: Frontend/src/components/shell/LeftRail/LeftRail.tsx
 
 import { For, Show, type JSX } from "solid-js";
-import { Plus } from "../../../lib/icons";
 import { railItems, type RailItem } from "../data/shell.data";
 import styles from "./LeftRail.module.scss";
 
@@ -77,14 +76,6 @@ export const LeftRail = (props: LeftRailProps): JSX.Element => {
 					</For>
 				</div>
 			</Show>
-
-			<Show when={!props.collapsed}>
-				<div class={styles.bottomCluster}>
-					<button type="button" class={styles.addButton} aria-label="Create server" title="Create server">
-						<Plus size={16} strokeWidth={2} />
-					</button>
-				</div>
-			</Show>
 		</aside>
 	);
 };