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/client.go

@@ -7,7 +7,7 @@ import (
 	"strings"
 	"time"
 
-	"cs-agent/internal/pkg/errorsx"
+	"bosschat/internal/pkg/errorsx"
 
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 )
@@ -116,7 +116,7 @@ func (c *Client) connect(ctx context.Context, cfg ServerConfig) (*mcp.ClientSess
 		},
 	}
 	client := mcp.NewClient(&mcp.Implementation{
-		Name:    "cs-agent-mcp-client",
+		Name:    "bosschat-mcp-client",
 		Version: "v1",
 	}, nil)
 	transport := &mcp.StreamableClientTransport{