Fix getUniformRun

[Craig Macomber (Microsoft) (CraigMacomber)]

Description

Fix a bug in buildNodeComparator where it mishandled optional fields.

This results in fixing a user facing bug in FormattedText.Members.getUniformRun.

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[Craig Macomber (Microsoft) (CraigMacomber)]

I'd link this, but our API docs site is not up to date and FormattedText is missing. Seems like its multiple releases out of date?

[Joshua Smithrud (Josmithr)]

I'll investigate this later today.

[Copilot]

Pull request overview

This PR fixes a comparison bug in buildNodeComparator that could treat nodes as equal even when their optional fields (or even node types) differ, which surfaced as incorrect behavior in FormattedText.Members.getUniformRun.

Changes:

• Update buildNodeComparator to compare node types and to reject nodes with additional/missing fields (fixing optional-field handling).
• Add targeted unit tests covering optional formatting fields and comparator correctness for type/field mismatches.
• Add a changeset documenting the user-facing behavioral fix.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
packages/dds/tree/src/feature-libraries/cursorComparator.ts	Fix comparator logic to account for type and optional/extra fields (hot-path optimized).
packages/dds/tree/src/test/feature-libraries/cursorComparator.spec.ts	Add regression tests for type mismatch and additional-field rejection.
packages/dds/tree/src/test/text/textDomainFormatted.spec.ts	Add regression test for getUniformRun behavior when optional format fields differ across a boundary.
.changeset/fix-formatted-text-uniform-runs.md	Document the behavior change in release notes.

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Bundle size comparison

Base commit: 4b2f54d10f10a46d9ef1c09b5b89f8e9adc2c9cb
Head commit: c40bb42286a64a5e8e0cebc258e3e3837ea1ba41

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