add CLAUDE.md, .gitignore, fix statusIcon rendering

- Add CLAUDE.md with build workflow, project overview, and key patterns
- Add .gitignore to prevent committing binaries and IDE files
- Remove hub.exe from tracking (was accidentally committed)
- Fix statusIcon: use Unicode ● character instead of HTML entities
  that get double-escaped by Go html/template

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hub/internal/web/server.go

@@ -256,14 +256,5 @@ func statusColor(status string) string {
 }
 
 func statusIcon(status string) string {
-	switch status {
-	case "ok":
-		return "🟢" // green circle
-	case "warn":
-		return "🟡" // yellow circle
-	case "down", "fail":
-		return "🔴" // red circle
-	default:
-		return "⚪" // white circle
-	}
+	return "●"
 }