Promote SharedTree commit settlement APIs to beta and legacy

[Abram Sanderson (Abe27342)]

Description

Make SharedTree commit settlement available without opting into alpha APIs, so applications can observe whether local edits and transactions are applied or dropped after sequencing.

Promote CommitOutcome and LocalCommitEvents to beta, with exports through both /beta and /legacy. Add ChangeMetadataBeta and TreeBranchEventsBeta, and expose the narrower changed event on TreeViewBeta and UntypedTreeView.

Keep change serialization, advanced undo, and transaction-label metadata alpha. Existing public and alpha signatures and runtime behavior are unchanged.

Include regenerated API reports for @fluidframework/tree and fluid-framework, a changeset, and coverage for beta/legacy transaction and merged-commit settlement.

Reviewer Guidance

The review process is outlined in the pull request guidelines.

Please review the boundary between the beta settlement metadata and the existing richer alpha metadata. API Council approval is required for the beta promotion.

[github-actions]

Hi! Thank you for opening this PR. Want me to review it?

Based on the diff (347 lines, 18 files), I've queued these reviewers:

• Correctness — logic errors, race conditions, lifecycle issues
• Security — vulnerabilities, secret exposure, injection
• API Compatibility — breaking changes, release tags, type design
• Performance — algorithmic regressions, memory leaks
• Testing — coverage gaps, hollow tests

How this works

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[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

$ start-server-and-test "npm run serve -- --host 127.0.0.1 --no-open" http://127.0.0.1:3000 check-links
1: starting server using command "npm run serve -- --host 127.0.0.1 --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-website@0.0.0 serve
> docusaurus serve --host 127.0.0.1 --no-open

[SUCCESS] Serving "build" directory at: http://127.0.0.1:3000/

> fluid-framework-website@0.0.0 check-links
> linkcheck http://127.0.0.1:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  658102 links
    3579 destination URLs
    3898 URLs ignored
       0 warnings
       0 errors

[github-actions]

Bundle size comparison

Base commit: 9a5d6f30a74c2626fad81ae3663994024125294a
Head commit: 2d2110e5c622d34cd062f7dea0f681aeaa2e0a9f

Notable changes

No bundles changed by ≥ 500 bytes parsed.

Per-bundle deltas

@fluid-example/bundle-size-tests

• fluidFrameworkAllAlpha.js: parsed 801533 → 801589 (+56), gzip 220527 → 220600 (+73)
• azureClient.js: parsed 634336 → 634331 (-5), gzip 169989 → 170075 (+86)
• odspClient.js: parsed 606600 → 606711 (+111), gzip 163052 → 163198 (+146)
• aqueduct.js: parsed 533117 → 533128 (+11), gzip 143294 → 143338 (+44)
• fluidFramework.js: parsed 415378 → 415411 (+33), gzip 117810 → 117845 (+35)
• sharedTree.js: parsed 404757 → 404783 (+26), gzip 115252 → 115271 (+19)
• containerRuntime.js: parsed 315027 → 315009 (-18), gzip 86438 → 86439 (+1)
• sharedString.js: parsed 170105 → 170112 (+7), gzip 48455 → 48462 (+7)
• experimentalSharedTree.js: parsed 161846 → 161846 (0), gzip 46722 → 46722 (0)
• matrix.js: parsed 153720 → 153727 (+7), gzip 44381 → 44388 (+7)
• loader.js: parsed 147328 → 147344 (+16), gzip 40038 → 40049 (+11)
• odspDriver.js: parsed 106695 → 106753 (+58), gzip 33227 → 33293 (+66)
• directory.js: parsed 65669 → 65676 (+7), gzip 18493 → 18502 (+9)
• 578.js: parsed 58686 → 58686 (0), gzip 17657 → 17657 (0)
• odspPrefetchSnapshot.js: parsed 46463 → 46444 (-19), gzip 15512 → 15522 (+10)
• map.js: parsed 45820 → 45827 (+7), gzip 14120 → 14127 (+7)
• 252.js: parsed 44384 → 44384 (0), gzip 13741 → 13741 (0)
• summarizerDelayLoadedModule.js: parsed 31287 → 31287 (0), gzip 7929 → 7929 (0)
• socketModule.js: parsed 27108 → 27078 (-30), gzip 8069 → 8103 (+34)
• createNewModule.js: parsed 12464 → 12464 (0), gzip 4792 → 4805 (+13)
• summaryModule.js: parsed 3888 → 3888 (0), gzip 1874 → 1874 (0)
• connectionState.js: parsed 909 → 909 (0), gzip 500 → 500 (0)
• sharedTreeAttributes.js: parsed 845 → 852 (+7), gzip 496 → 505 (+9)
• debugAssert.js: parsed 429 → 429 (0), gzip 299 → 299 (0)
• FluidFramework-HashFallback.js: parsed 419 → 419 (0), gzip 313 → 313 (0)