fix(gui): polish sidebar layout, wordmark, tooltip, and fonts to figma

Fixed sidebar width (never concedes), figma session-row rail (16px twist +
status slots, triangle arrows, mount fade), exact brand wordmark svg with
tooltip'd rail controls, form controls inheriting the app font stack, and
inlined the twist button reset since the tsdown CSS pipeline drops composes.

packages/client/ui-primitives/src/Tooltip.module.css

@@ -0,0 +1,38 @@
+/* Visual spec mirrors deepsuite @deepseek/ui Tooltip.css (size m, no arrow),
+   except padding tightened 6/12 -> 4/8 and radius 10 -> 8 by product ruling:
+   tooltip-bg plate,
+   one text color across both themes (the plate stays dark in light and dark
+   mode). Behavior (fixed positioning off the anchor rect) is local — the
+   upstream Floating stack is intentionally not vendored. */
+
+.bubble {
+  position: fixed;
+  z-index: 100;
+  padding: 4px 8px;
+  border-radius: 8px;
+  background: var(--dsw-alias-tooltip-bg);
+  color: var(--dsw-static-neutral-bluish-00);
+  font-size: 14px;
+  line-height: 22px;
+  white-space: nowrap;
+  pointer-events: none;
+  animation: tooltip-in 150ms var(--ds-ease-in-out);
+}
+
+.bubble[data-side='right'] {
+  transform: translateY(-50%);
+}
+
+.bubble[data-side='bottom'] {
+  transform: translateX(-50%);
+}
+
+@keyframes tooltip-in {
+  from { opacity: 0; }
+}
+
+@media (prefers-reduced-motion: reduce) {
+  .bubble {
+    animation: none;
+  }
+}