refactor: Export isFinalId from id-compressor internally and reference it in SharedTree

[Abe27342]

Description

Replaces explicit checks against 0 for short ids with isFinalId, exporting it from the /internal entrypoint.

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Exports isFinalId from the id-compressor /internal entrypoint and replaces inline >= 0 / < 0 checks in SharedTree with it for clarity.

Changes:

• Export isFinalId from id-compressor /internal and add @internal + @privateRemarks docs.
• Replace explicit short-id sign checks with isFinalId calls in SharedTree codecs.
• Remove related TODO comments.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/runtime/id-compressor/src/index.ts	Re-exports isFinalId.
packages/runtime/id-compressor/src/identifiers.ts	Adds @internal and explanatory privateRemarks to isFinalId.
packages/dds/tree/src/feature-libraries/chunked-forest/codec/nodeEncoder.ts	Uses isFinalId for narrowing.
packages/dds/tree/src/feature-libraries/chunked-forest/codec/chunkDecoding.ts	Uses isFinalId on stream value.
packages/dds/tree/src/core/tree/detachedFieldIndexCodecV2.ts	Replaces sign checks with isFinalId.
packages/dds/tree/src/core/tree/detachedFieldIndexCodecV1.ts	Replaces sign checks with isFinalId.

[github-actions]

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