fix(query): honor per-operation useMutation override for GET operations

A per-operation `override.operations.<id>.query.useMutation: true` was
silently discarded for GET operations: the operation stayed a Query
hook instead of becoming a Mutation hook. This was the inverse
asymmetry of the per-operation `useQuery: true` path, which already
worked for non-GET verbs.

`effectiveUseMutation` already encodes the per-verb default
(`verb !== Verbs.GET`), so the extra `&& verb !== Verbs.GET` gate on
`isMutation` only ever suppressed an explicit opt-in. Drop the gate so
`isMutation` honors explicit intent for every verb, mirroring how
`isQuery` honors `useQuery: true` for non-GET verbs.

Closes #3358

Author: wadakatu

docs/content/docs/reference/configuration/output.mdx

@@ -693,11 +693,20 @@ restriction for individual operations.
 
 **Type:** `Boolean`
 
-**Default:** `true` for non-`GET` operations.
-
-Generate `useMutation` hooks for non-`GET` operations. Set to `false`
-to suppress Mutation hook generation; pair with `useQuery: true` if
-you want non-`GET` operations to be generated as Query hooks instead.
+**Default:** `true` for non-`GET` operations; `false` otherwise.
+
+Generate `useMutation` hooks. When set explicitly, applies to **all
+operations regardless of HTTP verb** — setting `useMutation: true`
+(globally or via `override.operations.<id>.query.useMutation`) routes
+a `GET` operation to a `useMutation` hook as well. This is useful for
+`GET` endpoints that you want to trigger imperatively rather than on
+render.
+
+Set to `false` to suppress Mutation hook generation; pair with
+`useQuery: true` if you want non-`GET` operations to be generated as
+Query hooks instead. When both `useQuery` and `useMutation` resolve to
+`true` for the same operation, the Mutation hook wins for `GET` and the
+Query hook wins for non-`GET`.
 
 ### useInfinite
 

packages/query/src/query-generator.ts

@@ -833,7 +833,12 @@ export const generateQueryHook = async (
     effectiveUseInfinite ||
     effectiveUseSuspenseInfiniteQuery;
 
-  let isMutation = effectiveUseMutation && verb !== Verbs.GET;
+  // No verb gate here: `effectiveUseMutation` already encodes the
+  // per-verb default (`verb !== Verbs.GET`), so an explicit
+  // `useMutation: true` — global or per-operation — must be honoured for
+  // GET operations too, mirroring how `isQuery` honours `useQuery: true`
+  // for non-GET verbs (#3358).
+  let isMutation = effectiveUseMutation;
 
   // If both query and mutation are true for a non-GET operation, prioritize query
   if (verb !== Verbs.GET && isQuery) {