Document the package, exported constants, and remaining helpers.

godoc now covers ActionAdd/ActionDelete, internal helpers, and UDP-then-TCP UPDATE behaviour.

Co-authored-by: Cursor <cursoragent@cursor.com>

axfr.go

@@ -71,6 +71,7 @@ func (c *Client) AXFR(ctx context.Context) (*TransferResult, error) {
 	}, nil
 }
 
+// tsigAlgorithm maps a BIND algorithm name to miekg/dns constants.
 func tsigAlgorithm(name string) string {
 	trimmed := strings.ToLower(strings.TrimSpace(name))
 	trimmed = strings.TrimSuffix(trimmed, ".")
@@ -92,6 +93,7 @@ func tsigAlgorithm(name string) string {
 	}
 }
 
+// timeoutFrom uses the context deadline, or 30s, with a 1s floor.
 func timeoutFrom(ctx context.Context) time.Duration {
 	deadline, ok := ctx.Deadline()
 	if !ok {