feat(cli): TUI component architecture — status bars, message list, input bar

- Split monolithic app.tsx into composable components:
  - TopBar: connection indicator (●/○), gateway URL, model name, conversation ID
  - BottomBar: cwd, git branch, token usage
  - MessageList: timestamped messages, tool call indicators, thinking display
  - InputBar: context-aware prompt with streaming/disconnect states
- Extract socket logic into useSocket hook with typed events
- Extract git/cwd info into useGitInfo hook
- Quiet disconnect: single indicator instead of error flood
- Add @mosaic/types dependency for typed Socket.IO events
- Add PRD and task tracking docs

Tasks: TUI-001 through TUI-007 (Wave 1)

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

@@ -0,0 +1,55 @@
+import React from 'react';
+import { Box, Text } from 'ink';
+
+export interface TopBarProps {
+  connected: boolean;
+  connecting: boolean;
+  gatewayUrl: string;
+  conversationId?: string;
+  modelName: string | null;
+}
+
+export function TopBar({
+  connected,
+  connecting,
+  gatewayUrl,
+  conversationId,
+  modelName,
+}: TopBarProps) {
+  const indicator = connected ? '●' : '○';
+  const indicatorColor = connected ? 'green' : connecting ? 'yellow' : 'red';
+
+  const statusLabel = connected ? 'connected' : connecting ? 'connecting' : 'disconnected';
+
+  // Strip protocol for compact display
+  const host = gatewayUrl.replace(/^https?:\/\//, '');
+
+  return (
+    <Box borderStyle="single" borderColor="gray" paddingX={1} justifyContent="space-between">
+      <Box>
+        <Text bold color="blue">
+          mosaic
+        </Text>
+        <Text> </Text>
+        <Text color={indicatorColor}>{indicator}</Text>
+        <Text dimColor> {statusLabel}</Text>
+        <Text dimColor> · {host}</Text>
+      </Box>
+      <Box>
+        {modelName && (
+          <>
+            <Text dimColor>model: </Text>
+            <Text color="magenta">{modelName}</Text>
+            <Text> </Text>
+          </>
+        )}
+        {conversationId && (
+          <>
+            <Text dimColor>conv: </Text>
+            <Text>{conversationId.slice(0, 8)}</Text>
+          </>
+        )}
+      </Box>
+    </Box>
+  );
+}