fix(playground): search instruments by label

[misaelalves99]

Summary

• Fix the playground instrument selector's search to match visible instrument labels while preserving instrument UUIDs as selection values.
• Update the playground page object to search by label before selecting an instrument.
• Add an end-to-end regression test for searching Form Reference by its visible label.

Fixes #1764.

Validation

• RED: Regression test failed as expected because the instrument option was not found when filtering by its label.
• GREEN: Regression test passed after the fix.
• Playground E2E: 9/9 Chromium tests passed.
• Static checks: Prettier, targeted ESLint, playground TypeScript, and testing TypeScript checks passed.
• Playground Vitest: Passed.

Testing limitations

• The repository-wide production build was blocked by the API's RELEASE_VERSION requirement.
• The isolated playground production build encountered a Node.js heap out-of-memory error.
• The repository-wide CI suite was not executed locally.