Enabled unicorn/no-array-reduce in packages/tree

[brrichards]

Removes the unicorn/no-array-reduce: off override from the @fluidframework/tree package and fixes the resulting errors. Converts all Array.reduce() calls to explicit for loops. This is part of an ongoing effort to incrementally remove global ESLint rule overrides from eslint.config.mts and .eslintrc.cjs.

Changes:

• Production code (2 files)
• Test code (6 files)

No inline overrides were needed - all reduce usages could be converted to for loops.

[Copilot]

Pull request overview

This PR removes the unicorn/no-array-reduce ESLint rule override from the @fluidframework/tree package and converts all Array.reduce() calls to explicit for loops, improving code readability and debuggability.

• Removes the ESLint rule override from both eslint.config.mts and .eslintrc.cjs
• Converts 8 different reduce() operations across 8 files to explicit for loops
• All conversions maintain logical equivalence with improved clarity

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/dds/tree/eslint.config.mts	Removes unicorn/no-array-reduce: "off" override
packages/dds/tree/.eslintrc.cjs	Removes unicorn/no-array-reduce: "off" override
packages/dds/tree/src/test/simple-tree/list.spec.ts	Converts reduce in prettyArgs() to for loop for string building
packages/dds/tree/src/test/shared-tree-core/edit-manager/editManagerScenario.ts	Converts reduce for finding minimum peer reference to explicit Math.min with spread
packages/dds/tree/src/test/feature-libraries/sequence-field/utils.ts	Converts reduce in composeDeep() to for loop for composing changes
packages/dds/tree/src/test/feature-libraries/optional-field/optionalChangeRebaser.test.ts	Converts reduce in rebaseComposedWrapped() to for loop for composing changesets
packages/dds/tree/src/test/feature-libraries/modular-schema/modularChangesetUtil.ts	Converts reduce in fieldChangeMapFromDescription() to for-of loop
packages/dds/tree/src/test/core/tree/anchorSet.spec.ts	Converts reduce in makePath() to for-of loop for building path structure
packages/dds/tree/src/shared-tree-core/editManager.ts	Converts two reduce operations in loadSummaryData() to for loops for building commit chains
packages/dds/tree/src/core/rebase/utils.ts	Converts reduce in rebaseChangeOverChanges() to for loop for rebasing changes