feat: add Behavior settings page for global AGENTS.md (#1079)

* feat: add Behavior settings page for global AGENTS.md

- Add new 'Behavior' settings page to manage global system prompt
- Sync global behavior prompt to ~/.config/opencode/AGENTS.md
- Add GET/PUT /api/behavior/agents-md endpoints with 1MB size limit
- Add AbortController guards and parallel fetches in BehaviorPage
- Add i18n translations for en, es, ko, pt-BR, uk, zh-CN
- Add globalBehaviorPrompt to DesktopSettings type and sanitizer
- Add /api/behavior to express.json() body-parser whitelist
- Ensure atomic save: AGENTS.md written before settings updated

* fix: address Greptile review feedback

- Rename misleading 'trimmed' variable to 'value' in settings-helpers.js
- Add Content-Length guard for /api/behavior before 50mb JSON parser
- Use express.json({ limit: '1mb' }) for behavior endpoints
- Add actual translations for es, ko, pt-BR, uk, zh-CN locales

* fix(vscode): support behavior settings endpoint

* fix(behavior): wait for settings persistence

* fix(behavior): end agents file with newline

* fix(behavior): avoid duplicate textarea resize handles

* fix(behavior): clarify global rules copy

* fix(behavior): move rules note into tooltip

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/components/views/SettingsView.tsx

@@ -30,11 +30,13 @@ import {
   RiRestartLine,
   RiServerLine,
   RiSlashCommands2,
+  RiBrainLine,
 } from '@remixicon/react';
 import { Tooltip, TooltipContent, TooltipTrigger } from '@/components/ui/tooltip';
 import { ErrorBoundary } from '@/components/ui/ErrorBoundary';
 import { AgentsSidebar } from '@/components/sections/agents/AgentsSidebar';
 import { AgentsPage } from '@/components/sections/agents/AgentsPage';
+import { BehaviorPage } from '@/components/sections/behavior/BehaviorPage';
 import { CommandsSidebar } from '@/components/sections/commands/CommandsSidebar';
 import { CommandsPage } from '@/components/sections/commands/CommandsPage';
 import { McpSidebar } from '@/components/sections/mcp/McpSidebar';
@@ -93,6 +95,7 @@ const pageOrder: SettingsPageSlug[] = [
   'projects',
   'remote-instances',
   'agents',
+  'behavior',
   'commands',
   'mcp',
   'providers',
@@ -140,6 +143,8 @@ export function getSettingsNavIcon(slug: SettingsPageSlug): React.ComponentType<
       return RiCloudLine;
     case 'agents':
       return RiAiAgentLine;
+    case 'behavior':
+      return RiBrainLine;
     case 'commands':
       return RiSlashCommands2;
     case 'mcp':
@@ -395,6 +400,8 @@ export const SettingsView: React.FC<SettingsViewProps> = ({ onClose, forceMobile
         return t('settings.page.usage.title');
       case 'agents':
         return t('settings.page.agents.title');
+      case 'behavior':
+        return t('settings.page.behavior.title');
       case 'commands':
         return t('settings.page.commands.title');
       case 'mcp':
@@ -478,6 +485,8 @@ export const SettingsView: React.FC<SettingsViewProps> = ({ onClose, forceMobile
         return <RemoteInstancesPage />;
       case 'agents':
         return <AgentsPage />;
+      case 'behavior':
+        return <BehaviorPage />;
       case 'commands':
         return <CommandsPage />;
       case 'mcp':