feat: unified hook notifier, agent auto-detection, terminal transition UI

- Add hooks/notify.ps1 as single hook handler for all events
- Refactor settings.local.json to use notify.ps1 instead of inline PS
- Add Notification hook, auto-detect agent from session_id/transcript
- Rename agent 'main' to 'claude' across server routes and terminal
- Add loading overlay and error state for terminal switching transitions
- Add transitionError ref to useTranscriptDebug composable

server/services/terminal.ts

@@ -23,7 +23,7 @@ interface AgentTerminalState {
 export const agentSessions = new Map<string, AgentTerminalState>()
 
 const AGENT_COMMANDS: Record<string, string> = {
-  'main': 'claude',
+  'claude': 'claude',
   'ejecutor': 'ejecutor',
   'nucleo000': 'nucleo000'
 }
@@ -695,7 +695,7 @@ type ClaudeStatus = 'idle' | 'thinking' | 'toolUse' | 'reading' | 'writing' | 's
 
 // Broadcast Claude status to ALL clients across ALL sessions
 export function broadcastClaudeStatus(status: ClaudeStatus, tool?: string, agent?: string) {
-  const agentName = agent || 'main'
+  const agentName = agent || 'claude'
 
   // Track agent running state
   if (status === 'sessionStart') {