refactor: express flag-boundary check as a single regex

Author: claude

internal/docgen/mintlify.go

@@ -189,16 +189,13 @@ func backtickFlags(s string) string {
 	return strings.Join(parts, "```")
 }
 
-// isFlagBoundaryChar reports whether c is a valid character before a flag —
-// anything that is not a word char (\w), backtick, slash, or dash.
+// nonBoundaryByte matches a single byte that cannot precede a CLI flag:
+// a word char (\w), backtick, slash, or dash.
+var nonBoundaryByte = regexp.MustCompile("[`/\\w-]")
+
+// isFlagBoundaryChar reports whether c is a valid character before a flag.
 func isFlagBoundaryChar(c byte) bool {
-	switch {
-	case c == '/', c == '-', c == '`', c == '_':
-		return false
-	case c >= 'a' && c <= 'z', c >= 'A' && c <= 'Z', c >= '0' && c <= '9':
-		return false
-	}
-	return true
+	return !nonBoundaryByte.Match([]byte{c})
 }
 
 func backtickFlagsFragment(s string) string {