refactor(managed-agent): split Agent and Session stores (#16090)

* test(managed-agent): audit lock order across store collaborators

Record the bilingual Store decomposition contract and entry ownership,
transaction, lock and caller inventories. Follow final collaborator fields
across source files while preserving owner-bound facade populations and
existing ambiguity, transaction and compiled-member checks.

Co-authored-by: Qwen-Coder <[email protected]>

* refactor(managed-agent): split Agent and Session stores

Move Agent and Journal responsibilities into immutable internal collaborators while retaining transaction facades and compatibility bridges. Resolve Journal dependencies at construction and migrate factories, fixtures, lock auditing and the bilingual implementation contract.

Record focused verification and outstanding full-gate requirements separately.

Co-authored-by: Qwen-Coder <[email protected]>

* fix(managed-agent): repair store decomposition verification

Keep declared field receivers visible across method-local type scopes while retaining fail-closed nested class handling. Preserve the Hosted CSI dependency identity assertion at its new owner.

Co-authored-by: Qwen-Coder <[email protected]>

---------

Co-authored-by: Qwen-Coder <[email protected]>

scripts/tests/managed-agent-server-e2e.test.js

@@ -1905,7 +1905,7 @@ describe('managed-agent-server e2e runner', () => {
     expect(source).toContain(`'${refusal}'`);
     expect(
       read(
-        'packages/managed-agent-server/persistence/src/main/java/com/alibaba/qwen/code/managedagent/persistence/ManagedSessionStore.java',
+        'packages/managed-agent-server/persistence/src/main/java/com/alibaba/qwen/code/managedagent/persistence/JournalFencing.java',
       ),
     ).toContain(`"${refusal}."`);
     const writerBefore = source.indexOf(