fix: unions used as a request or response body generate typed instead of any

[giraffesyo]

What

A oneOf/anyOf schema used directly as a request or response body generated any. It now generates the same typed union the generator already produces elsewhere.

The synthesis path existed and worked; it was simply never reached from bodies. synthesizeInlineUnion returns false without a naming hint, and the body path resolved with an empty one:

// operations.go, before
return a.resolveGoType(schema, "")

This threads the operation's Go name down through convertRequestBody, convertResponses, convertSingleResponse, and resolveMediaTypeSchema, so a body union is named <Operation>Body or <Operation>Response.

Titled unions name themselves

Synthesized unions are deduplicated by variant refs and discriminator, so a union shared by several operations is named after whichever one the spec reaches first. That is order-dependent: inserting a route earlier renames existing generated types, which is churn for consumers that diff-gate their SDK.

So a title on the union now wins over the operation hint. A spec that names its unions gets stable names regardless of route order; a spec that does not still improves from any.

Effect on a real spec

Against the Parallel Works API (754 types), before:

func (c *Client) GetClusterAttachedStorages(...) (*[]any, error)
func (c *Client) AttachClusterStorage(..., body any) (*[]any, error)
func (c *Client) GetClusterDefinition(...) (*any, error)

after, with title set on the two attached-storage unions and nothing else changed:

func (c *Client) GetClusterAttachedStorages(...) (*[]AttachedStorage, error)
func (c *Client) AttachClusterStorage(..., body AttachedStorageWrite) (*[]AttachedStorage, error)
func (c *Client) GetClusterDefinition(...) (*GetClusterDefinitionResponse, error)

The generated union carries the discriminator-driven UnmarshalJSON, so decoding yields the concrete variant rather than a map.

Tests

testdata/complex-schemas.yaml gains two paths: one with untitled union bodies, one titled. New tests assert the untitled bodies take the operation hint, that an identical union elsewhere still deduplicates, and that a titled union uses its title and does not also emit a hint-named type. The exact-count assertion in TestComplexSchemas_AllTypesPresent is updated for the three new synthesized types.

Note this changes generated output for any spec with union bodies: those signatures move from any to a named type. That is the point, but it is a visible diff for consumers on regeneration.