refactor: move the transport onto the official Gitea SDK

The transport was hand-rolled net/http against the REST API. The payload shapes
were ours, in internal/wire, which meant every field Gitea learned was a field
somebody here had to notice; and "does this instance have issue dependencies?"
had to be guessed from a status code, because a 404 from a missing route and a
404 from a missing issue look alike.

The SDK settles both. The shapes are maintained by the people who maintain the
server, and the client negotiates the server's version when it is built, so the
dependency endpoint is now gated on `>= 1.20.0` — verified against the release
where the route appears, not assumed. Below the gate nothing is requested at all.

internal/wire keeps what the SDK has no answer for: addressing. The SDK takes an
owner, a name and an int64 and never parses, while `42`, `#42`, `owner/repo#42`
and an issue URL are four spellings of one address, all four are what somebody
has in hand, and Key is what the ledger is keyed by. The payload structs go.

Four things that had to survive the move, and did:

- request bodies still land in .kettle/payload/, now via an http.RoundTripper on
  the client the SDK is given — which is better than before, because it files
  every request rather than the ones a call site remembered to name;
- errors still carry the HTTP status AND the response body, and a decode failure
  on a 2xx is deliberately not an APIError, so the dependency probe cannot read
  a bad decode as "feature missing";
- the number -> slug ledger is untouched, entries still outlive the files they
  name;
- Client.For(repo) still re-points at another repository for one call.

What it cost, written down in AGENTS.md where it happened. internal/mapping's
layering test was a fact about the import graph — nothing in its closure could
open a socket — and the SDK ships its types and its client in one package, so
the test now asserts what is still true: the bridge performs no I/O, checked on
direct imports plus a grep for time.Now. A run makes one extra request before it
does anything. Gitea's issue edit endpoint carries no labels, so a push whose
labels changed needs a second call; push makes it and says so. go.mod requires
go 1.26, which the SDK sets and which is now the floor for building this binary.

internal/issue and internal/project are byte-identical. The domain did not
notice, which is the whole argument for the layering.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

cli/internal/mapping/labels.go

@@ -3,8 +3,9 @@ package mapping
 import (
 	"strings"
 
+	sdk "code.gitea.io/sdk/gitea"
+
 	"git.noodles.cam/claude-skills/marketplace/cli/internal/issue"
-	"git.noodles.cam/claude-skills/marketplace/cli/internal/wire"
 )
 
 // How the taxonomy is painted in Gitea's UI. A hex code says nothing about what
@@ -43,20 +44,22 @@ func LabelColor(name string) string {
 
 // LabelSpecs is the request body for each name, in the order given.
 //
-// A wire.LabelRequest and not a shape of this package's own: it is field for
-// field what a label create takes, and a second spelling of it would mean the
-// bootstrap command copying four fields across on its way to the transport.
+// The SDK's own CreateLabelOption and not a shape of this package's own: it is
+// field for field what a label create takes, and a second spelling of it would
+// mean the bootstrap command copying four fields across on its way to the
+// transport. It is what an EDIT is built from too — see Client.EditLabel — so
+// one value says what a label should be, whether or not it exists yet.
 // Exclusivity and meaning come from the domain taxonomy; only the color is
 // decided here.
 //
 // A slice and not a map: the order is the taxonomy's, and a bootstrap prints
 // its plan in that order — a map would shuffle the plan on every run and make
 // two identical runs look like different ones.
-func LabelSpecs(names []string) []wire.LabelRequest {
+func LabelSpecs(names []string) []sdk.CreateLabelOption {
 	ns := exclusiveNamespaces()
-	out := make([]wire.LabelRequest, 0, len(names))
+	out := make([]sdk.CreateLabelOption, 0, len(names))
 	for _, name := range names {
-		out = append(out, wire.LabelRequest{
+		out = append(out, sdk.CreateLabelOption{
 			Name:        name,
 			Color:       LabelColor(name),
 			Description: typeMeaning(name),
@@ -72,7 +75,7 @@ func LabelSpecs(names []string) []wire.LabelRequest {
 // Derived from the domain's own list rather than restated: add a type over in
 // the taxonomy and the next bootstrap creates it, with no line changing here
 // except the color it is painted with.
-func CanonicalLabelSpecs() []wire.LabelRequest { return LabelSpecs(issue.CanonicalLabels()) }
+func CanonicalLabelSpecs() []sdk.CreateLabelOption { return LabelSpecs(issue.CanonicalLabels()) }
 
 // exclusiveNamespaces are the namespaces at most one label may come from, read
 // off the canonical set rather than listed again — the domain publishes exactly