feat(cli): match TUI footer to reference design

- Remove borders from input bar — clean '❯ message mosaic…' prompt
- Two-line footer without borders:
  - Line 1: compact cwd (branch) | Gateway: Connected/Disconnected
  - Line 2: token stats (^in v_out R_cache W_cache $cost ctx%) | (provider) model
- Extend TokenUsage with cacheRead, cacheWrite, cost, contextPercent, contextWindow
- Add providerName to socket hook return
- Reorder layout: top bar → messages → input → footer

packages/cli/src/tui/components/input-bar.tsx

@@ -26,12 +26,10 @@ export function InputBar({ onSubmit, isStreaming, connected }: InputBarProps) {
       ? 'waiting for response…'
       : 'message mosaic…';
 
-  const promptColor = !connected ? 'red' : isStreaming ? 'yellow' : 'green';
-
   return (
-    <Box paddingX={1} borderStyle="single" borderColor="gray">
-      <Text bold color={promptColor}>
-        ❯{' '}
+    <Box paddingX={0}>
+      <Text bold color="green">
+        {'❯ '}
       </Text>
       <TextInput
         value={input}