refactor(api): split monolithic handlers.go into focused modules

Break down the 627-line handlers.go into specialized modules:
- handlers_chat.go: chat and streaming endpoints
- handlers_config.go: configuration endpoints
- handlers_common.go: shared utilities
- handlers_info.go: info and status endpoints
- handlers_terminal.go: terminal/shell endpoints
- handlers_tools.go: tool-related endpoints

Also includes config improvements, orchestrator enhancements, and
web component updates.

💘 Generated with Crush

Assisted-by: MiniMax-M2.7 via Crush <crush@charm.land>

internal/api/server.go

@@ -43,6 +43,8 @@ func (s *Server) routes() {
 	s.mux.HandleFunc("/api/ws/terminal", s.handleTerminalWS)
 	s.mux.HandleFunc("/api/terminal/sessions", s.handleTerminalSessions)
 	s.mux.HandleFunc("/api/terminal/sessions/", s.handleTerminalSessionsDelete)
+	s.mux.HandleFunc("/api/terminal/themes", s.handleGetTerminalThemes)
+	s.mux.HandleFunc("/api/terminal/settings", s.handleSaveTerminalSettings)
 	s.mux.HandleFunc("/api/mcp/configure", s.handleMCPConfigure)
 	s.mux.HandleFunc("/api/config/profile", s.handleSaveProfile)
 	s.mux.HandleFunc("/api/config/provider", s.handleSaveProvider)