DNSSEC: say where the DS record really goes

The DNSSEC tab said "give this to your registrar" for every zone whose
parent wasn't in Jarl in the same view. The DNSSEC response now has
ds_at/ds_place/ds_note: the parent zone in Jarl (any view, its own
first, then a public one), the registrar for a registered domain, the
parent zone wherever it is hosted for a subdomain, the ISP or RIR for a
reverse zone, and nowhere for a private name. The page and the CLI use
them.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/api.md

@@ -294,11 +294,20 @@ view ([dnssec.md](dnssec.md#what-jarl-refuses-and-why)).
   },
   "named": {"secure": true, "inline_signing": true, "serial": 2026100802, "signed_serial": 2026100804, "next_key_event": "..."},
   "policies": ["default"],
-  "parent_zone": "",          // set when the parent zone is a primary zone in Jarl
+  "ds_at": "registrar",       // parent_zone, registrar, parent, reverse or none
+  "ds_place": "at your registrar", // completes "add the DS record ..."
+  "ds_note": "",              // for ds_at none: why it can't have one
+  "parent_zone": "",          // set when the parent zone is a primary zone in Jarl (any view, its own first)
   "registrar": "porkbun"      // when the DS can be published through Jarl
 }
 ```
 
+`ds_at` says where the DS record goes ([dnssec.md](dnssec.md#should-you-sign)):
+`parent_zone` (a zone in Jarl: `parent_zone`, `parent_zone_id`,
+`parent_view`), `registrar` (the zone is a registered domain), `parent` (a
+subdomain whose parent zone is hosted elsewhere), `reverse` (whoever
+delegates the addresses) or `none` (nothing on the internet delegates it).
+
 `phase.code` is one of `off`, `leftover_keys`, `starting`, `signing`,
 `ready`, `ds_pending`, `secure`, `removing_ds`, `ds_expiring`,
 `removing_keys`, `unsigned` ([dnssec.md](dnssec.md#phases)).

docs/dnssec.md

@@ -30,6 +30,17 @@ Signing an internal-only zone (one no registrar delegates, or a split-DNS
 view only your own network reaches) adds nothing. There is no parent to
 publish a DS, and BIND doesn't validate the zones it serves itself.
 
+**Where the DS record goes** depends on the zone. The DNSSEC tab and
+`jarl zone dnssec status` say which:
+
+| Zone | The DS record goes |
+|---|---|
+| a registered domain (`adbraun.lol`) | at your registrar ([Porkbun](#porkbun) can do it for you) |
+| a subdomain whose parent zone is in Jarl (`lab.adbraun.lol`) | in the parent zone, as a DS record named `lab`: one button, or the `jarl record add` command shown. The parent in the zone's own view counts first, else one in another view (a public one first). |
+| a subdomain whose parent zone is hosted elsewhere | in that parent zone, wherever it is hosted (at Porkbun: the domain's DNS records) |
+| a reverse zone | with whoever delegates it to you: your ISP, or your RIR for an address block of your own. Many ISPs don't take DS records. |
+| a private name (`home.lan`) | nowhere: nothing on the internet delegates it, so signing it has no effect |
+
 **Split DNS.** In Jarl a zone belongs to a view, so you sign the external
 view's `adbraun.lol` and leave the internal view's copy unsigned. That is
 the usual setup, with one catch. Once the DS is at the parent, the world