fix(hooks): cycle useTreeFocus typeahead on repeated letters

[alex-js-ltd]

Resolves #4843.

Problem

useTreeFocus has its own typeahead implementation, which has drifted from the shared useTypeahead behavior.

This causes three related issues:

• repeated letters build queries like "aa" instead of cycling through matches;
• with no focused treeitem, the first match is searched last;
• multi-character queries skip the current item even when it still matches.

For example, pressing p twice quickly in the FullyExpanded TreeList story stalls on public instead of advancing to package.json.

Fix

Align useTreeFocus with the typeahead semantics being established in #3797:

• repeated characters collapse back to a single-character query;
• search ordering now distinguishes between cycling a single character and refining a multi-character query.

No public API changes.

Tests

Added regression coverage for all three cases:

• repeated-letter cycling;
• searching from the first item when nothing is focused;
• keeping focus when the current item still matches a refined query.

Before the fix: 3 failing, 13 passing
After the fix: 16 passing

Also verified the full ui test suite (6472/6472 passing), Prettier, ESLint, core typecheck, and check:changesets.

Reproduce manually

Open the [FullyExpanded story](https://facebook.github.io/astryx/storybook/index.html?path=/story/core-treelist--fully-expanded), click a row, then press p twice quickly.

Before: focus stops on public.
After: focus advances to package.json.

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[github-actions]

PR Analysis Report

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No new or modified components detected.

Bundle Size Summary

Package	Size (ESM)	Size (CJS)	Gzipped
@astryxdesign/core	N/A	4.7KB	1.2KB

Accessibility Audit

Status: No accessibility violations detected.

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