refactor: rebrand from cs-agent to BossChat

- Rename Go module: cs-agent → bosschat
- Rename all import paths across 200+ Go files
- Rename SDK: cs-ai-agent-sdk → bosschat-sdk
- Rename message protocol: cs-agent:* → bosschat:*
- Rename JS globals: CSAgentConfig → BossChatConfig
- Rename CSS classes: cs-agent-* → bosschat-*
- Update Makefile APP_NAME and ARCHIVE_NAME
- Update logo assets
- Fix display name: BoosChat → BossChat

internal/ai/mcps/server.go

@@ -20,8 +20,8 @@ func NewHTTPHandler() http.Handler {
 
 func newServer() *mcp.Server {
 	server := mcp.NewServer(&mcp.Implementation{
-		Name:       "cs-agent-mcp-server",
-		Title:      "CS Agent MCP Server",
+		Name:       "bosschat-mcp-server",
+		Title:      "BossChat MCP Server",
 		Version:    "v1",
 		WebsiteURL: "https://github.com/modelcontextprotocol",
 	}, nil)