GeezerVison

Brings in oapi-codegen#2587 (a reusable form response's envelope is marshalled, not
its wrapper) and oapi-codegen#2589 (types from an imported document qualify only
their model names).

Co-Authored-By: Claude Opus 5.5 <[email protected]>

The fixture oapi-codegen#2589 added has a reusable response whose schema is
`x-go-type: "*string"`, reached only from `default`. Its envelope now
carries a Body field, as a pointer envelope does, so that a
fixed-status $ref to it would compile.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* fix: wrap receiver-incompatible strict JSON responses

* test: cover strict JSON response receiver compatibility

* test: cover strict JSON response wire values

* test: cover OpenAPI 3.1 strict JSON responses

* fix: keep strict response shapes that already compile

Wrapping every receiver-incompatible body changed response types that
compiled before, breaking code written against them:

- A components/responses envelope is never a method receiver. Each
  operation that reaches it through $ref embeds it in a struct, and an
  embedded field may be an interface, so an untyped or interface
  envelope compiled as a direct type. Only a pointer, which cannot be
  embedded, needs a Body field there.

- Under schema-merging-behavior v1, an allOf of a single $ref becomes
  a struct that embeds the member, which is a valid receiver, whether
  it is inline or a component of its own. The single-member allOf
  shortcut assumed the member's type is always used directly.

Classify a composition by a referenced member only when the generator
actually emitted that member's type. That also covers a nullable union
collapsed to an untyped member, and an allOf of an untyped $ref with
sibling keywords under v3. Check the declared type of x-go-type-name
as well.

One envelope that compiled before still changes: a pointer envelope
that no operation reaches through a fixed-status $ref, so that it is
never embedded (only reached through default, a status range, or not
at all), goes from `type FooJSONResponse *T` to a struct with a Body
field. The envelope has to match what a fixed-status $ref needs, and
no generated operation uses the envelope in that case.

servers/strict/responsebody_v1 compiles and serves the v1 shapes.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* fix: wrap untyped text and form strict response bodies

A text/plain or application/x-www-form-urlencoded response without a
schema, or with one that lowers to any, generated a method on an
interface type, the same compile error as the JSON case:

    invalid receiver type GetText200TextResponse (pointer or interface type)

The strict templates already write text and form bodies from
response.Body whenever the response has a Body field, so classify
these content types as well.

An operation that reaches a reusable text response through $ref
redeclares its envelope as the receiver type, unlike a JSON or form
envelope, which it embeds. So a text envelope is classified as a
receiver.

That changes one type that compiled before: a reusable text envelope
whose body lowers to any or a pointer, and that no operation reaches
through a fixed-status $ref (only through default, a status range, or
not at all), goes from `type FooTextResponse any` to a struct with a
Body field. A fixed-status $ref to it needs that shape to compile, and
no generated operation uses the envelope otherwise.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* refactor: drop NeedsLocalResponseHeaders

NeedsLocalResponseHeaders only restated `not .IsRef`, and the strict
templates used it for two of their three header branches; the branch
for a response without content still reads $isRef. It changes no
output, so go back to $isRef throughout and keep the templates' diff
to what the fix needs.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* test: describe what the response_cast fixture now covers

The spec headers still described only the #2010 cast. Name the
untyped, pointer and header-bearing responses the fixture now covers,
and cite #2525 alongside #1328.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* test: pin the v1 wire bodies, and spell the nullable fixtures with anyOf

Review follow-ups:

- responsebody_v1 only checked that the direct responses were valid
  JSON, so a visitor that dropped the value would still pass. Assert
  the body. v1 embeds the untyped member, and encoding/json encodes an
  embedded interface as a field named after its type, so the value
  has always gone out as {"Untyped": ...}. The test records that.

- Untyped ({}) already admits null, so oneOf of it and a null branch
  rejects null, the value the fixtures send. Use anyOf, which the
  generator lowers identically, in both fixtures. The unit test keeps
  the oneOf spelling that specs commonly use, and adds the anyOf one.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

* test: regenerate external_types for reusable pointer envelopes

The fixture #2589 added has a reusable response whose schema is
`x-go-type: "*string"`, reached only from `default`. Its envelope now
carries a Body field, as a pointer envelope does, so that a
fixed-status $ref to it would compile.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

---------

Co-authored-by: Marcin Romaszewicz <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>