fix: restyle environment selector to match DS TopBar pill

Make the select transparent (no border, no background) so it
inherits the DS .env pill styling (success-colored badge with
mono font). Negative margins compensate for the pill padding.
Dropdown chevron uses currentColor to match the pill text.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/EnvironmentSelector.module.css

@@ -1,26 +1,27 @@
 .select {
   appearance: none;
   background: transparent;
-  border: 1px solid var(--border);
-  border-radius: 4px;
-  padding: 2px 20px 2px 6px;
-  font-size: 11px;
-  color: var(--text-muted);
+  border: none;
+  padding: 0;
+  margin: -3px -10px;
+  font-family: var(--font-mono);
+  font-size: 10px;
+  font-weight: 600;
+  color: inherit;
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
   cursor: pointer;
   outline: none;
-  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6' viewBox='0 0 10 6'%3E%3Cpath d='M1 1l4 4 4-4' stroke='%23888' fill='none' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
+  line-height: 1;
+  padding-right: 14px;
+  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='8' height='5' viewBox='0 0 8 5'%3E%3Cpath d='M1 1l3 3 3-3' stroke='currentColor' fill='none' stroke-width='1.5' stroke-linecap='round' stroke-linejoin='round'/%3E%3C/svg%3E");
   background-repeat: no-repeat;
-  background-position: right 5px center;
-  background-size: 10px 6px;
-  min-width: 80px;
-  line-height: 1.4;
-}
-
-.select:hover {
-  border-color: var(--text-muted);
+  background-position: right 0 center;
+  background-size: 8px 5px;
 }
 
 .select:focus-visible {
-  border-color: var(--accent);
-  box-shadow: 0 0 0 1px var(--accent);
+  outline: 1px solid var(--accent);
+  outline-offset: 4px;
+  border-radius: 2px;
 }