Implement per-orchestration and per-activity versioning

[torosent]

Summary

What changed?

• Implemented per-orchestration and per-activity versioning across the abstractions, worker runtime, gRPC worker, in-proc sidecar, and source generator surfaces.
• Added version-aware routing and migration support for orchestrators and activities, including explicit ActivityOptions.Version overrides, inherited version fallback behavior, ContinueAsNew version migration, and strict worker-version filter handling.
• Added and updated focused samples and tests, including the activity versioning sample and unit/integration coverage for explicit version selection, fallback behavior, tag propagation, and review follow-ups.
• Removed the local-only docs/superpowers planning/spec artifacts from the branch diff.

Why is this change needed?

• The SDK needs task-level version selection so orchestrations and activities can evolve independently without forcing users onto worker-level versioning semantics.
• Explicit activity version selection must be strict for correctness, while inherited orchestration-version activity routing still needs compatibility fallback to existing unversioned registrations.
• This PR moves the implementation from the design/proposal stage in #692 to a working end-to-end implementation with generator, runtime, sample, and test coverage.

Issues / work items

• Resolves Per-Task Versioning: Architecture Proposal #692
• Related: none

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Project checklist

• Release notes are not required for the next release
  • Otherwise: Notes added to release_notes.md
• Backport is not required
  • Otherwise: Backport tracked by issue/PR #issue_or_pr
• All required tests have been added/updated (unit tests, E2E tests)
• Breaking change?
  • If yes:
    • Impact:
    • Migration guidance:

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AI-assisted code disclosure (required)

Was an AI tool used? (select one)

• No
• Yes, AI helped write parts of this PR (e.g., GitHub Copilot)
• Yes, an AI agent generated most of this PR

If AI was used:

• Tool(s): GitHub Copilot CLI (GPT-5.4)
• AI-assisted areas/files:
  • src/Abstractions/*
  • src/Worker/Core/*
  • src/Worker/Grpc/*
  • src/InProcessTestHost/*
  • src/Grpc/orchestrator_service.proto
  • test/Worker/Core.Tests/*
  • test/Grpc.IntegrationTests/*
  • samples/*versioning*
• What you changed after AI output:
  • Drove the implementation through multiple review/debug cycles, tightened explicit activity-version semantics, fixed tag propagation gaps in the in-proc sidecar/protobuf path, added stricter regression coverage, and removed local-only planning docs from the PR.

AI verification (required if AI was used):

• I understand the code and can explain it
• I verified referenced APIs/types exist and are correct
• I reviewed edge cases/failure paths (timeouts, retries, cancellation, exceptions)
• I reviewed concurrency/async behavior
• I checked for unintended breaking or behavior changes

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Testing

Automated tests

• Result: Passed
• dotnet build Microsoft.DurableTask.sln --nologo --verbosity minimal
• dotnet test test/Worker/Core.Tests/Worker.Tests.csproj --nologo --verbosity minimal
• dotnet test test/Worker/Grpc.Tests/Worker.Grpc.Tests.csproj --nologo --verbosity minimal
• dotnet test test/Grpc.IntegrationTests/Grpc.IntegrationTests.csproj --filter "FullyQualifiedName~VersionedClassSyntaxIntegrationTests" --nologo --verbosity minimal

Manual validation (only if runtime/behavior changed)

• Environment (OS, .NET version, components): macOS, .NET SDK 10.0.5, gRPC worker, in-proc sidecar/integration host
• Steps + observed results:
  1. Scheduled versioned orchestrations with explicit versions and observed routing to the matching class-based implementation.
  2. Executed explicit activity-version override scenarios and observed exact-match routing with no fallback to unversioned registrations.
  3. Executed inherited activity-version scenarios and observed compatibility fallback to unversioned activity registrations when no explicit activity version was requested.
• Evidence (optional):
  • Integration coverage in VersionedClassSyntaxIntegrationTests

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Notes for reviewers

• Explicit activity-version strictness relies on ActivityRequest.tags; sidecars outside this repo need matching support to preserve the same semantics end-to-end.
• The PR includes the review follow-ups that protect the internal explicit-version tag from user spoofing and keep TaskScheduledEvent.Tags in the in-proc protobuf path.

[torosent]

Closing this draft and recreating it from the requested branch: torosent/orchestration-versioning.