Cap distributed directory ownership transfer batch size

[ReubenBond]

Summary

Stabilizes distributed grain directory ownership transfer so this can be the first merge candidate in the directory PR sequence.

This PR is now limited to the foundational ownership-transfer fixes:

• correct snapshot handoff range selection
• stable ownership checks while partition transfers are in flight

Details

When a partition acquires a range, that range can span multiple previous owners. The acquiring partition now requests snapshots only for the intersection between the acquired range and each previous owner's actual range, instead of asking any previous owner for unrelated parts of the ring.

Directory register/lookup/deregister operations now wait against a stable ownership view before deciding whether the local partition can serve a request. This avoids stale-membership requests racing with a newer in-flight range transfer and being served by a partition that is no longer the correct owner.

Changes

• Request snapshot transfer only for the intersection of previousOwnerRange and addedRange.
• Add targeted coverage for snapshot transfer range intersections.
• Wait for stable current ownership before partition RegisterAsync, LookupAsync, and DeregisterAsync responses.

Stack notes

• Add distributed remote grain directory compatibility #10050 is rebased on top of this branch and contains the IRemoteGrainDirectory compatibility implementation.
• Batch large directory transfer payloads #10053 is stacked above Add distributed remote grain directory compatibility #10050 for large transfer payload batching.
• Add directory migration join regression #10049 is stacked above Batch large directory transfer payloads #10053 for the directory migration join regression.

Focused branch ranges:

• Cap distributed directory ownership transfer batch size #10047: main..fix/directory-snapshot-transfer-ranges
• Add distributed remote grain directory compatibility #10050: fix/directory-snapshot-transfer-ranges..feature/distributed-remote-grain-directory
• Batch large directory transfer payloads #10053: feature/distributed-remote-grain-directory..fix/directory-transfer-payload-batching
• Add directory migration join regression #10049: fix/directory-transfer-payload-batching..fix/directory-migration-regression-test

Validation

Focused validation run locally:

• dotnet test test\Orleans.GrainDirectory.Tests\Orleans.GrainDirectory.Tests.csproj --framework net10.0 --filter "FullyQualifiedName~GrainDirectoryPartitionTests" -- -parallel none -noshadow
• dotnet test test\Orleans.GrainDirectory.Tests\Orleans.GrainDirectory.Tests.csproj --framework net10.0 --filter "FullyQualifiedName~GrainDirectoryRollingUpgradeTests|FullyQualifiedName~GrainDirectoryPartitionBatchingTests|FullyQualifiedName~GrainDirectoryResilienceTests.JoiningSilo_DoesNotLeaveStaleEntriesOnPreviousOwner" -- -parallel none -noshadow

GrainDirectoryResilienceTests.ElasticChaos was also attempted as part of a broader top-stack run and timed out after several minutes; the narrower non-chaos coverage above passed.

[Copilot]

Pull request overview

Fixes distributed grain directory snapshot transfers so that range pulls are scoped to the intersection of (a) the range being acquired and (b) the range owned by each previous owner, avoiding out-of-range snapshot requests during directory migration.

Changes:

• Expand DEBUG assertions to account for full-range membership cases during range transitions.
• Adjust range-acquisition snapshot pulls to request only previousOwnerRange ∩ addedRange (including wrapped-range intersections).
• Update trace/warning log message text to reflect singular “range” wording.

Show a summary per file

File	Description
src/Orleans.Runtime/GrainDirectory/GrainDirectoryPartition.cs	Restricts snapshot transfer queries to the prior owner’s actual owned subrange intersecting the acquired range; minor assertion/log message adjustments.

Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 2

[ReubenBond]

Rebuilt this as the first green merge candidate. It now contains the coupled lower-layer fixes needed for CI to pass from main:

• snapshot transfer range intersections (Cap distributed directory ownership transfer batch size #10047)
• stable ownership checks previously in Stabilize directory ownership checks #10048
• the base DistributedGrainDirectory / IRemoteGrainDirectory compatibility commit needed by the heterogeneous silo upgrade SlowBVTs

The rolling-upgrade regression test was moved to the later feature PR layer because it depends on the follow-up resilience commits there.