Per-tenant managed partitioning parity with Marten (documents + streams)

[jeremydmiller]

Follow-up epic to the Wolverine conjoined EF Core multi-tenancy epic (JasperFx/wolverine#3465). Depends on the Weasel parity work in JasperFx/weasel#362.

Polecat supports Weasel ManagedTenantPartitions for the events table only (UseTenantPartitionedEvents, #163/#171, with per-tenant sequences via TenantEventSequenceRegistry). Marten's per-tenant partitioning goes further, and Polecat should reach full equivalence:

Gaps vs Marten today

• Document tables: conjoined documents are tenant_id column + filter only. DocumentTable explicitly throws when partitioning is combined with conjoined tenancy ("RANGE partitioning of document tables is currently supported for single-tenant tables only"). Marten offers managed tenant partitioning on all conjoined document tables.
• Streams table: Marten partitions mt_streams alongside mt_events under UseTenantPartitionedEvents; audit what pc_streams does and bring it in line.
• Policy APIs: no equivalents of Marten's AllDocumentsAreMultiTenantedWithPartitioning(...) / PartitionMultiTenantedDocumentsUsingMartenManagement(...).
• Runtime tenant onboarding: no equivalent of store.Advanced.AddMartenManagedTenantsAsync(...) / RemoveMartenManagedTenantsAsync(...) returning TablePartitionStatus[], nor the reserved default-tenant partition Marten auto-provisions for global projections.

Proposed scope

1. Lift the DocumentTable restriction: managed tenant partitioning for conjoined document tables (tenant_ordinal column + the store's shared ManagedTenantPartitions feature, one registry per database).
2. Partition the streams table to match the events table under UseTenantPartitionedEvents.
3. Policy-level API parity (naming TBD, mirroring Marten's shapes).
4. Runtime API parity: store.Advanced.AddPolecatManagedTenantsAsync(...) / Remove... with per-table status returns; reserved default-tenant partition if the Marten global-projection behavior applies.
5. Define tenant-removal data semantics — SQL Server MERGE RANGE does not remove the tenant's rows (see ManagedTenantPartitions (SQL Server) parity with ManagedListPartitions: drop semantics, bucketing, back-fill weasel#362 item 1).

This epic is the prerequisite for CritterWatch's SQL Server hard-delete support (JasperFx/CritterWatch#68).