Deprecate IIdCompressorCore ahead of making it internal in 2.100

[markfields]

Resolves AB#63316

Description

IIdCompressorCore was always meant to be an internal detail, not exposed in any API surface to consumers. It leaked due to free functions createIdCompressor and deserializeIdCompressor including it in their return type, as well as the utility of the serialize function on the interface.

This PR deprecates it, including a migration plan in the changeset.

To see the final state we'll release in 2.100.0, see 94bfedf

Breaking Changes

None, this is merely deprecating / announcing the upcoming change. See #26903

[markfields]

Marked as release-blocking since Monday's release is the deadline for these announcements for 2.100.0

[Copilot]

Pull request overview

This PR deprecates IIdCompressorCore in @fluidframework/id-compressor and introduces a migration path so consumers can continue serializing compressors without depending on the core interface ahead of the planned 2.100.0 internalization.

Changes:

• Marked IIdCompressorCore as deprecated and added migration guidance in TSDoc and a changeset.
• Added serializeIdCompressor(compressor, withSession) as the supported serialization API for consumers.
• Added an internal helper (toIdCompressorWithCore) to support internal runtime usage while preparing to narrow return types in a future release.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/runtime/id-compressor/src/types/idCompressor.ts	Adds deprecation + migration guidance on IIdCompressorCore.
packages/runtime/id-compressor/src/index.ts	Exports new serialization helper and internal cast helper.
packages/runtime/id-compressor/src/idCompressor.ts	Adds new free-function serialization API and internal cast helper; updates docs around return-type narrowing.
packages/runtime/id-compressor/api-report/id-compressor.legacy.beta.api.md	Updates legacy beta API report to reflect deprecation + new function exports.
.changeset/deprecate-id-compressor-core.md	Documents the deprecation and migration steps in release notes.

[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:
  272202 links
    1863 destination URLs
    2108 URLs ignored
       0 warnings
       0 errors

[CraigMacomber]

Approving changeset for docs.

[jason-ha]

Deprecations should reference a GitHub issue. If there is a planned time for the break, then it should be associated with breaking change issue for that version. I don't see an issue (should be linked here) and don't see anything under #26282 which covers 2.100 breaks.

[markfields]

Yes thanks for the reminder I'll open an issue today