Implemented E2E test for clearing all labels from an issue. ## Changes Made - Created new test file: tests/e2e/test_update_issue_clear_all_labels.py ## Test Coverage The new test file contains 9 test cases covering the following scenarios: 1. Clear all labels from an issue with a single label 2. Clear all labels from an issue with multiple labels 3. Verify placeholder text 'Labels' shows after clearing 4. Verify count badge hides after clearing all labels 5. Verify cleared labels persist after page refresh 6. Verify canceling after clearing discards changes 7. Verify cleared labels show as unchecked in dropdown 8. Clear all labels then add new label in same session 9. UI state tracking during the label clearing process ## Verification All 9 tests pass locally with the E2E server running. ## Implementation Notes - Follows existing patterns from test_update_issue_remove_label.py and test_update_issue_clear_assignee_to_null.py - Tests the MultiSelectDropdown component used for labels - Verifies both UI behavior and API persistence