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/constants/brain-project.ts

@@ -0,0 +1,69 @@
+/**
+ * Multi-project Brain constants
+ */
+
+export const BRAIN_PROJECT = {
+  MAX_PROJECTS: 100,
+  NAME_MIN_LENGTH: 2,
+  NAME_MAX_LENGTH: 100,
+  DESCRIPTION_MAX_LENGTH: 500,
+  DEFAULT_RECALL_LIMIT: 5,
+  DEFAULT_SYNC_INTERVAL: 30, // minutes
+} as const;
+
+export const BRAIN_PROJECT_STORAGE = {
+  CONFIG_FILE: "brain-projects.json",
+  EXPORT_EXTENSION: ".brain-export.json",
+  BACKUP_EXTENSION: ".brain-backup.json",
+} as const;
+
+export const BRAIN_PROJECT_PATHS = {
+  LOCAL: ".codetyper/brain",
+  GLOBAL: "~/.local/share/codetyper/brain",
+  EXPORTS: "~/.local/share/codetyper/brain/exports",
+  BACKUPS: "~/.local/share/codetyper/brain/backups",
+} as const;
+
+export const BRAIN_PROJECT_COMMANDS = {
+  LIST: "/brain projects",
+  CREATE: "/brain project create",
+  SWITCH: "/brain project switch",
+  DELETE: "/brain project delete",
+  EXPORT: "/brain project export",
+  IMPORT: "/brain project import",
+  SYNC: "/brain project sync",
+} as const;
+
+export const BRAIN_PROJECT_API = {
+  LIST: "/api/projects",
+  CREATE: "/api/projects",
+  GET: "/api/projects/:id",
+  UPDATE: "/api/projects/:id",
+  DELETE: "/api/projects/:id",
+  SWITCH: "/api/projects/:id/switch",
+  EXPORT: "/api/projects/:id/export",
+  IMPORT: "/api/projects/import",
+  SYNC: "/api/projects/:id/sync",
+} as const;
+
+export const BRAIN_PROJECT_MESSAGES = {
+  CREATED: "Brain project created successfully",
+  SWITCHED: "Switched to project",
+  DELETED: "Brain project deleted",
+  EXPORTED: "Brain project exported",
+  IMPORTED: "Brain project imported",
+  SYNCED: "Brain project synced",
+  NOT_FOUND: "Brain project not found",
+  ALREADY_EXISTS: "Project with this name already exists",
+  INVALID_NAME: "Invalid project name",
+  SWITCH_FAILED: "Failed to switch project",
+  EXPORT_FAILED: "Failed to export project",
+  IMPORT_FAILED: "Failed to import project",
+} as const;
+
+export const BRAIN_PROJECT_DEFAULTS = {
+  AUTO_LEARN: true,
+  AUTO_RECALL: true,
+  CONTEXT_INJECTION: true,
+  SYNC_ENABLED: false,
+} as const;