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/mcp/mcp.go

@@ -53,7 +53,7 @@ func ScanServers() []MCPServer {
 
 func getCoreEntries(homeDir string) []mcpEntry {
 	return []mcpEntry{
-		{"filesystem", "npx", []string{"-y", "@modelcontextprotocol/server-filesystem", homeDir + "/projects"}, nil},
+		{"filesystem", "npx", []string{"-y", "@modelcontextprotocol/server-filesystem", filepath.Join(homeDir, "projects")}, nil},
 		{"fetch", "npx", []string{"-y", "@modelcontextprotocol/server-fetch"}, nil},
 		{"memory", "npx", []string{"-y", "@modelcontextprotocol/server-memory"}, nil},
 	}
@@ -86,7 +86,9 @@ func writeMCPConfig(configPath string, mcpKey string, entries []mcpEntry) error
 	existing := map[string]interface{}{}
 	data, err := os.ReadFile(configPath)
 	if err == nil {
-		json.Unmarshal(data, &existing)
+		if err := json.Unmarshal(data, &existing); err != nil {
+			return fmt.Errorf("parse existing config: %w", err)
+		}
 	}
 
 	mcpMap := map[string]interface{}{}