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>

go.mod

@@ -1,6 +1,8 @@
 module github.com/muyue/muyue
 
-go 1.24.3
+go 1.24.2
+
+toolchain go1.24.3
 
 require (
 	github.com/charmbracelet/huh v1.0.0