[Feature Request] HTTP: support the QUERY method (RFC 10008) and OpenAPI 3.2 `query` operation emission

## Clear and concise description of the problem

The HTTP `QUERY` method is now a Proposed Standard — [RFC 10008](https://www.rfc-editor.org/rfc/rfc10008.html) (published June 2026, from `draft-ietf-httpbis-safe-method-w-body`). It provides safe, idempotent request semantics like `GET`, but carries the query in the request body — the long-standing answer to "GET with a body" / oversized query strings.

OpenAPI 3.2.0 already supports it as a **first-class path-item operation** (`query:`), alongside the new `additionalOperations` field.

TypeSpec currently cannot express this method:

- `HttpVerb` in `@typespec/http` is `"get" | "put" | "post" | "patch" | "delete" | "head"` ([types.ts](https://github.com/microsoft/typespec/blob/main/packages/http/src/types.ts)) — no `query`.
- Notably, the OpenAPI 3.2 **document model** in `@typespec/openapi3` already includes it: `OpenAPIHttpMethod3_2 = OpenAPI3HttpMethod | "query"` plus `additionalOperations` on `OpenAPIPathItem3_2` (types.d.ts). So the emitter-side representation exists — the gap is purely on the authoring side (verb decorator + `HttpVerb`), and presumably the converter/emit wiring.

Since `@typespec/openapi3` can already emit `openapi: 3.2.0` documents (`openapi-versions: [3.2.0]`), this seems like a natural, well-scoped completion of the existing 3.2 support.

## Describe the solution you'd like

1. Add `"query"` to `HttpVerb` in `@typespec/http`.
2. Add a verb decorator. Naming needs design input, since `@query` is already the query-*parameter* decorator in the same namespace. Options: `@httpQuery`, or a generic escape hatch like `@verb("query")` (which would also serve issue #2866 for `OPTIONS`, and future methods via OpenAPI 3.2 `additionalOperations`).
3. Emission rules in `@typespec/openapi3`:
- Target `3.2.0`: emit as first-class `query:` operation.
- Targets `3.0.x` / `3.1.x`: report a diagnostic (these versions have a closed operation set; `additionalOperations` is 3.2-only).
4. (Optional, symmetric) `tsp-openapi3` convert: map `query:` operations in 3.2 documents back to the new verb.

Related: #2866 (OPTIONS verb support, `design:needed`) — a generic `@verb(...)` design could resolve both, though QUERY differs in that it deserves first-class treatment given its RFC status and first-class OpenAPI 3.2 slot.

I'm happy to contribute the implementation once the decorator naming/design is settled.

## Checklist

- [x] Follow our [Code of Conduct](https://github.com/microsoft/typespec/blob/main/CODE_OF_CONDUCT.md)
- [x] Read the [docs](https://typespec.io/docs).
- [x] Search for [existing issues](https://github.com/microsoft/typespec/issues) to avoid creating duplicates.

Begin with packages/http/src/types.ts and the @typespec/openapi3 types.d.ts model, then trace the existing verb decorator and converter/emitter wiring. Confirm how HTTP verbs reach OpenAPI path-item operations and where version-specific diagnostics are tested. Done means QUERY is authorable, emits as query for OpenAPI 3.2, and is diagnosed for earlier versions.

Written by the indexing model from the issue text.