[niemyjski]

Daily and monthly index names now use Gregorian dates regardless of the process culture, matching the existing parser. Both nested date-formatting calls explicitly use CultureInfo.InvariantCulture. Previously, Thai and Arabic calendars could produce names that maintenance interpreted as future or ancient Gregorian partitions.

Validation: 30 synthetic culture tests pass (12 failed before the fix), 152 local core tests pass, and the full Release solution builds with zero warnings/errors using published package dependencies. Independent Astra review found no blockers. Exact-head CI passed all 869 tests, including the Elasticsearch suite, on its first attempt. Local checks used no live services; hosted integration tests used CI containers.

Rollout warning: Existing culture-generated physical indexes and aliases are not automatically migrated and remain susceptible to incorrect date interpretation. Review affected deployments before rollout; this PR does not rename, delete, or migrate existing indexes or aliases.

Verification and implementation details

• Covers exact daily/monthly physical names and aliases, producer/parser round trips, configured/explicit versions, and synthetic retention selection under en-US, de-DE, fr-FR, th-TH, and ar-SA.
• Baseline example for 2026-10-05: Thai produced events-v2-2569.10.05; Arabic produced events-v2-1448.04.24. Synthetic Gregorian maintenance skipped expired Thai partitions and selected a recent Arabic partition. Deletion was overridden to record names only, and test configuration rejects Elasticsearch client access.
• Culture scopes restore both current culture properties. Two obsolete assembly attributes were replaced with xUnit 4's equivalent Parallelization(Mode = None) because current main's xUnit package rejects the old properties at compile time. Test parallelization remains disabled; dependencies and workflows are unchanged.
• Build: dotnet build Foundatio.Repositories.slnx --configuration Release -p:ReferenceFoundatioSource=false -p:ReferenceFoundatioRepositoriesSource=false.
• Focused tests: dotnet tests/Foundatio.Repositories.Elasticsearch.Tests/bin/Release/net10.0/Foundatio.Repositories.Elasticsearch.Tests.dll -class Foundatio.Repositories.Elasticsearch.Tests.TimeSeriesIndexCultureTests.
• Core tests: dotnet tests/Foundatio.Repositories.Tests/bin/Release/net10.0/Foundatio.Repositories.Tests.dll.
• Local runtime: .NET SDK 10.0.401 / runtime 10.0.12; library builds include net8.0 and net10.0. Full Elasticsearch integration tests were not run locally.
• Hosted CI verified head 5ee616b79bf8dcd6e65e10113c3f8f93ddcad16d: 869 passed, 0 failed, 0 skipped; build had zero warnings/errors. Packaging and both publishing steps were skipped.