[Bug] Broken persistence examples (scylla-ledger snapshotPolicy, cassandra-plugin-hello import path)

[pathosDev]

Two persistence examples do not compile / crash at runtime:

• examples/persistence/scylla-ledger.ts:43 overrides snapshotPolicy as a property (override readonly snapshotPolicy = everyNEvents(50)), but the base declares a method snapshotPolicy(): SnapshotPolicy (src/persistence/PersistentActor.ts:77). At runtime this.snapshotPolicy() calls a policy with zero args → TypeError on the first persist. Check benchmarks/persistence/recovery.ts for the same pattern.
• examples/persistence/cassandra-plugin-hello.ts:24 imports ../../tests/unit/persistence/FakeCassandraClient.js; after the tests/ split (Tests: split tests/ into unit/ + integration/ subtrees #295) the file lives at tests/integration/in-process/persistence/. Also replace the removed ask usage.

Drives the persistence share of the typecheck:dev error count down (currently 259 total).

Part of Phase 1.