fix(control-plane): reload memories when search is cleared

[oldnicke]

Fixes #3670.

When a zero-result text search was cleared, the Memories view kept the stale zero-result response and incorrectly replaced the search UI with the unfiltered empty-bank state.

This change explicitly reloads the unfiltered graph when an active query is cleared, while preserving tag/scope filters. The empty-bank state is also deferred while that reload is in flight so the search controls remain visible.

Validation:

• ./scripts/hooks/lint.sh
• npx tsc --noEmit
• npm test -- --run tests/lib/search-query.test.ts
• ./.githooks/pre-commit

The full control-plane suite has one pre-existing date-sensitive failure in tests/lib/relative-time.test.ts; 143 tests pass.