Add BRAIN_DISABLED flag and fix Ollama tool call formatting

Features:
  - Add BRAIN_DISABLED feature flag to hide all Brain functionality
  - When enabled, hides Brain banner, status indicator, menu, and commands
  - Flag location: src/constants/brain.ts

  Fixes:
  - Fix Ollama 400 error by properly formatting tool_calls in messages
  - Update OllamaMessage type to include tool_calls field
  - Fix Brain menu keyboard not working (add missing modes to isMenuOpen)

  UI Changes:
  - Remove "^Tab toggle mode" hint from status bar
  - Remove "ctrl+t to hide todos" hint from status bar

  Files modified:
  - src/constants/brain.ts (add BRAIN_DISABLED flag)
  - src/types/ollama.ts (add tool_calls to OllamaMessage)
  - src/providers/ollama/chat.ts (format tool_calls in messages)
  - src/tui-solid/components/header.tsx (hide Brain UI when disabled)
  - src/tui-solid/components/status-bar.tsx (remove hints)
  - src/tui-solid/components/command-menu.tsx (filter brain command)
  - src/tui-solid/components/input-area.tsx (fix isMenuOpen modes)
  - src/tui-solid/routes/session.tsx (skip brain menu when disabled)
  - src/services/brain.ts (early return when disabled)
  - src/services/chat-tui/initialize.ts (skip brain init when disabled)

src/services/config.ts

@@ -44,23 +44,41 @@ const PROVIDER_ENV_VARS: Record<Provider, string> = {
  * Config state (singleton pattern using closure)
  */
 let configState: Config = getDefaults();
+let configLoaded = false;
+let configLoadPromise: Promise<void> | null = null;
 
 /**
- * Load configuration from file
+ * Load configuration from file (with caching)
  */
 export const loadConfig = async (): Promise<void> => {
-  try {
-    const data = await fs.readFile(FILES.config, "utf-8");
-    const loaded = JSON.parse(data);
-
-    // Clean up deprecated keys
-    delete loaded.models;
-
-    configState = { ...getDefaults(), ...loaded };
-  } catch {
-    // Config file doesn't exist or is invalid, use defaults
-    configState = getDefaults();
+  // Return cached config if already loaded
+  if (configLoaded) {
+    return;
   }
+
+  // If loading is in progress, wait for it
+  if (configLoadPromise) {
+    return configLoadPromise;
+  }
+
+  // Start loading
+  configLoadPromise = (async () => {
+    try {
+      const data = await fs.readFile(FILES.config, "utf-8");
+      const loaded = JSON.parse(data);
+
+      // Clean up deprecated keys
+      delete loaded.models;
+
+      configState = { ...getDefaults(), ...loaded };
+    } catch {
+      // Config file doesn't exist or is invalid, use defaults
+      configState = getDefaults();
+    }
+    configLoaded = true;
+  })();
+
+  return configLoadPromise;
 };
 
 /**