Document every exported symbol and how callers use the library.

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

axfr.go

@@ -9,13 +9,17 @@ import (
 	"github.com/miekg/dns"
 )
 
-// TransferResult is a completed AXFR plus SOA serial metadata.
+// TransferResult is a completed AXFR.
+// Serial is the SOA serial and is the same value stored on Zone.
 type TransferResult struct {
 	Zone   Zone
 	Serial uint32
 }
 
-// AXFR fetches the full zone over TCP, signed with the session TSIG key.
+// AXFR reads the full zone over TCP, signed with the session TSIG key.
+// It returns an error when ctx is done, the transfer fails, a record owner
+// is not ASCII, or the stream contains no SOA.
+// The closing SOA of the transfer is not appended again.
 func (c *Client) AXFR(ctx context.Context) (*TransferResult, error) {
 	if err := ctx.Err(); err != nil {
 		return nil, err