tree: Shared branches

[alex-pardes]

Description

This PR allows clients to create multiple branches which are shared by all clients.

This PR introduces new formats that are NOT meant to be used in production.

Breaking Changes

None

[Copilot]

Pull Request Overview

This PR introduces support for shared branches in the tree data structure. The feature allows clients to create multiple branches that are shared across all clients, enabling collaborative editing scenarios with branching workflows.

Key Changes:

• Added new vSharedBranches format version (100) for supporting shared branches functionality
• Extended ITreeAlpha interface with methods for creating and viewing shared branches
• Enhanced id-compressor test utilities to support deterministic seeding for shared branch testing

Reviewed Changes

Copilot reviewed 75 out of 76 changed files in this pull request and generated no comments.

File	Description
packages/runtime/id-compressor/src/test/idCompressorTestUtilities.ts	Added seed parameter to createAlwaysFinalizedIdCompressor for deterministic ID generation
packages/framework/fluid-framework/api-report/fluid-framework.alpha.api.md	Added shared branch methods to ITreeAlpha interface and new vSharedBranches format version
packages/dds/tree/src/test/utils.ts	Enhanced test utilities with seed support and version filtering for encoding tests
Various snapshot files	Added comprehensive test snapshots for the new vSharedBranches format

Comments suppressed due to low confidence (2)

packages/dds/tree/src/test/utils.ts:1

• The casting of random.uuid4() to SessionId bypasses type safety. Consider using a helper function that validates the UUID format before casting, or use the existing createSessionId() function to ensure proper type safety and validation.

/*!

packages/dds/tree/src/test/utils.ts:1

• Similar to the previous issue, this casting of random.uuid4() to SessionId bypasses type safety. Consider using a helper function or the existing createSessionId() function to maintain proper type validation.

/*!

[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> fluid-framework-docs-site@0.0.0 ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  235713 links
    1720 destination URLs
    1953 URLs ignored
       0 warnings
       0 errors