Fix marten#4665: CatchUpAsync dispatches on _tenantHighWater under per-tenant partitioning; bump to 2.8.2

[jeremydmiller]

Fixes JasperFx/marten#4665.

Bug

JasperFxAsyncDaemon.CatchUpAsync(CancellationToken) — the test-automation
catch-up path that Marten's ForceAllMartenDaemonActivityToCatchUpAsync
drives — used the store-global _highWater agent even when
_tenantHighWater was non-null.

Under per-tenant event partitioning the store-global `mt_events_sequence` is
never advanced (per-tenant `mt_events_sequence_{suffix}` values power
`mt_events.seq_id` instead). So _highWater.CheckNowAsync() leaves the
global high-water pinned at the unused sequence's last_value. Driving
catch-up off HighWaterMark() in that mode leaves every catch-up loop
stuck at zero — the test helper returned "success" while every async
projection was still behind.

The normally-running daemon already does the right thing (uses
_tenantHighWater via the polling loop and rebuildProjectionForTenant);
the test-automation CatchUpAsync was the one path still on the global
route.

Fix

When _tenantHighWater is non-null and the database implements
ICrossTenantRebuildSource (the partitioned-store contract — Marten's
MartenDatabase implements it), fan out per tenant. For each base shard:

• Discover every tenant the projection knows about via
  ICrossTenantRebuildSource.FindRebuildTenantsAsync.
• Activate the tenants in _tenantHighWater.PolledTenants and drive one
  vectorized poll to fetch fresh ceilings (batched — one poll round-trip
  per shard, not per tenant).
• For each (shard, tenant), build a tenant-scoped agent
  (asyncShard with { Name = asyncShard.Name.ForTenant(tenantId) }) and
  catch it up to that tenant's ceiling.

Mirrors the rebuildProjectionForTenant ceiling-lookup pattern that
already existed for per-tenant rebuilds.

Single-tenant stores and non-partitioned multi-tenant stores keep the
byte-for-byte global path. The dispatch is gated on
_tenantHighWater != null && Database is ICrossTenantRebuildSource — no
other behavior changes.

Version

2.8.0 → 2.8.2 (skipping 2.8.1 to avoid clashing with any local
prerelease lines).

Marten-side regression

JasperFx/marten#4673 ships
the failing reproduction (currently Skip'd to keep CI from hanging).
After this lands on NuGet and Marten bumps Directory.Packages.props to
2.8.2, the Marten regression test gets unskipped.

Verification

Step	Result
dotnet build src/JasperFx.Events/JasperFx.Events.csproj -f net9.0	clean
dotnet test src/EventStoreTests -f net9.0	72 / 72 ✅
dotnet test src/EventTests -f net9.0	351 / 351 ✅

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