fix(ui5-multi-combobox): handle composition with validation

[aleksandar-terziev]

JIRA: BGSOFUIRILA-4156

Prevent validation rollback from interrupting IME input composition by skipping
validation until composition ends. Update tests for
Korean/Japanese/Chinese composition scenarios.

[ui5-webcomponents-bot]

🚀 Deployed on https://pr-12501--ui5-webcomponents-preview.netlify.app

[Copilot]

Pull Request Overview

This PR fixes an issue where the MultiComboBox component incorrectly validates and rejects input during IME (Input Method Editor) composition for languages like Korean, Japanese, and Chinese. The fix prevents validation from running while composition is in progress, ensuring that intermediate composition states don't trigger error states or clear the input prematurely.

Key Changes

• Modified validation logic to skip when composition is active (_isComposing flag)
• Adjusted when _inputLastValue is updated to exclude composition states
• Moved valueBeforeAutoComplete assignment inside composition check to preserve typed text
• Refactored tests to use helper functions and added comprehensive validation scenarios

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
packages/main/src/MultiComboBox.ts	Added composition guards to validation logic and input tracking
packages/main/test/pages/MultiComboBox.html	Added test cases for Korean and Chinese with validation
packages/main/cypress/specs/MultiComboBox.cy.tsx	Refactored composition tests with helpers and added validation coverage

[ndeshev]

Looks good to me. Add a bit of information about the PR in the description, like "prevent validation and typeahead during composite language input". Add a JIRA reference (BGSOFUIRILA-4156) for traceability. Check the copilot suggestions for small improvements above.