fix(web): preserve instrument showcase tag options

[misaelalves99]

Summary

The Instrument Showcase Tags filter could lose options after a parent re-rendered while a search was active. Its tag options were derived from filteredInstruments, causing tags outside the narrowed results to disappear.

This change:

• Derives tag options from the full availableInstruments collection using useMemo, removing redundant state and effect logic.
• Adds a unit regression test for searching, parent re-rendering, and clearing the search.
• Adds a Playwright regression test covering the Remote Assignment dialog workflow.

Fixes #1692.

Validation

• Unit RED/GREEN: regression failed before the fix and passed afterward; 22/22 tests passed on GREEN.
• Playwright RED/GREEN: expected regression failure before the fix; 7/7 tests passed afterward, including setup and teardown.
• Remote Assignment E2E (Chromium): 14/14 passed, including setup and teardown.
• Global Vitest: 384/384 test files passed; 4,346 passing tests and 4 expected failures.
• Global coverage: 100% statements, branches, functions, and lines.
• TypeScript (web and testing), targeted ESLint, Prettier and Git diff checks passed.

Testing limitations

The Playwright runs used an isolated setup with reduced demo-data generation to avoid an initialization timeout under WSL2. The complete monorepo E2E suite was not executed.

The full pnpm lint workflow was not run because it performs automatic modifications; relevant TypeScript, ESLint and Prettier checks were performed separately without modifying files.

Ready for review. GitHub CI checks have passed; awaiting code owner review.