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/types/tui.ts

@@ -5,6 +5,7 @@
  */
 
 import type { ProviderModel } from "@/types/providers";
+import type { BrainConnectionStatus, BrainUser } from "@/types/brain";
 
 // ============================================================================
 // App Mode Types
@@ -28,7 +29,9 @@ export type AppMode =
   | "provider_select"
   | "learning_prompt"
   | "help_menu"
-  | "help_detail";
+  | "help_detail"
+  | "brain_menu"
+  | "brain_login";
 
 /** Screen mode for determining which view to show */
 export type ScreenMode = "home" | "session";
@@ -230,6 +233,7 @@ export interface SessionStats {
   outputTokens: number;
   thinkingStartTime: number | null;
   lastThinkingDuration: number;
+  contextMaxTokens: number;
 }
 
 // ============================================================================
@@ -270,6 +274,9 @@ export interface AppState {
   // Screen mode (home vs session)
   screenMode: ScreenMode;
 
+  // Interaction mode (agent, ask, code-review)
+  interactionMode: InteractionMode;
+
   // Input state
   inputBuffer: string;
   inputCursorPosition: number;
@@ -318,9 +325,20 @@ export interface AppState {
   // Suggestion prompts state
   suggestions: SuggestionState;
 
+  // Brain state
+  brain: {
+    status: BrainConnectionStatus;
+    user: BrainUser | null;
+    knowledgeCount: number;
+    memoryCount: number;
+    showBanner: boolean;
+  };
+
   // Actions
   setMode: (mode: AppMode) => void;
   setScreenMode: (screenMode: ScreenMode) => void;
+  setInteractionMode: (mode: InteractionMode) => void;
+  toggleInteractionMode: () => void;
   setInputBuffer: (buffer: string) => void;
   setInputCursorPosition: (position: number) => void;
   appendToInput: (text: string) => void;
@@ -389,6 +407,13 @@ export interface AppState {
   hideSuggestions: () => void;
   showSuggestions: () => void;
 
+  // Brain actions
+  setBrainStatus: (status: BrainConnectionStatus) => void;
+  setBrainUser: (user: BrainUser | null) => void;
+  setBrainCounts: (knowledge: number, memory: number) => void;
+  setBrainShowBanner: (show: boolean) => void;
+  dismissBrainBanner: () => void;
+
   // Computed
   isInputLocked: () => boolean;
 }