fix(spec,objectql): changeset is a MAJOR bump, and sweep the last findStream stub

Two defects found reviewing the retirement against the `spec-property-retirement`
checklist:

- The changeset declared `minor` for all four packages. Removing a REQUIRED
  method from a published contract interface is breaking — the skill says
  `major` for `@objectstack/spec`, and it is the house convention for every
  other `!` spec change in this major (`session-dual-source-c4`,
  `notification-dual-source-c3`). The driver packages drop a public method too,
  so they go major with it.
- `protocol-batch-atomic.test.ts` still carried a `findStream() { throw new
  Error('not implemented'); }` stub. It is typed `any`, so it compiles and is
  simply dead — but it is exactly the stub this issue exists to sweep, and
  leaving one behind lets the next reader infer the method still exists.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012C2cd7tL8QDoZ2QKN3djJ5

Author: claude

.changeset/data-driver-find-stream-retired.md

@@ -1,8 +1,8 @@
 ---
-"@objectstack/spec": minor
-"@objectstack/driver-sql": minor
-"@objectstack/driver-memory": minor
-"@objectstack/driver-mongodb": minor
+"@objectstack/spec": major
+"@objectstack/driver-sql": major
+"@objectstack/driver-memory": major
+"@objectstack/driver-mongodb": major
 ---
 
 refactor(spec,drivers)!: retire `IDataDriver.findStream` — a required method with no caller, whose two main implementations did the opposite of what it promised (#4484, ADR-0049 enforce-or-remove)

packages/objectql/src/protocol-batch-atomic.test.ts

@@ -49,7 +49,6 @@ function makeSnapshotDriver() {
         async checkHealth() { return true; },
         async execute() { return null; },
         async find(object: string) { return Array.from(storeFor(object).values()); },
-        findStream() { throw new Error('not implemented'); },
         async findOne(object: string, ast: any, options: any) {
             seen.findOne.push({ object, transaction: options?.transaction });
             const id = ast?.where?.id ?? ast?.filters?.id;