Fix network-event selection and verified task contracts

[lanyue-llk]

Summary

• evaluate navigation tasks against matching XHR/fetch requests instead of forcing every GET through the last document-navigation event
• opt task 676 into all-matching-event comparison so a later notification request cannot hide the target order-grid filter
• correct observed route contracts for GitLab issue filtering and Reddit forum submissions
• remove the impossible unchecked-checkbox field from task 475
• encode tasks 699/700 Magento form fields by their actual indexed names instead of invalid one-item alternatives
• increment every affected task revision and keep the published hard-task export aligned

Evidence

Saved HAR replay from two independent Chromium cohorts changes task 676 from 0 to 1 after the event-selection correction. Saved traces for tasks 339, 475, 600, and 625 also pass after their contract corrections.

Validation

• 5,648 non-environment tests passed; 6,391 skipped
• dataset integrity: 1,820 passed
• new focused regression tests: 6 passed
• Ruff check/format and ty check passed

The repository-wide default pytest command also invokes HF parity and live Docker environment suites without their required fixtures; those produced expected environment/configuration failures and are not included in the passing count above.

[lanyue-llk]

Superseded by #46, which carries the same validated commit from the lexmount organization fork.