Preserve active plugin workspace on refresh

[wowalxa2-tech]

Description

• wait for enabled Plugin registration before restoring the shell page
• persist the active Plugin Workspace in session storage and restore it after refresh
• fail closed for malformed, stale, unavailable, or incompatible saved panels
• clear saved Workspace state when returning home or closing the Workspace
• update generated frontend artifacts and regression coverage

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation
• Code style
• Refactoring
• Performance
• Tests
• Configuration

Related Issues

None.

Checklist

• Follows project style guidelines
• Ran black on Python code (not applicable; no Python changes)
• Ran eslint on JavaScript code (no ESLint script is defined)
• Fixed linter warnings/errors
• Tested locally
• Updated documentation if needed (not needed; public behavior and contracts are unchanged)
• No security vulnerabilities
• No sensitive information committed

Testing

1. npm run test:frontend — 98 passed
2. npm run check:frontend — generated frontend artifacts match
3. .venv/bin/python scripts/check-t8-docs.py — 26 required artifacts passed
4. git diff --check origin/main...HEAD — passed

Additional Notes

The PR contains one commit and six product/test files. Local Playwright logs, screenshots, and the unintegrated design prototype are intentionally excluded.

---

By submitting, I confirm:

• License contributions under MIT
• Understand checks must pass before merge