test-runner: remove blocking sync calls from remaining shell suites

[T72]

Summary

Several shell test suites still use sync in WSL paths (setup/cleanup), causing runner timeouts (timeout 60) despite assertions passing.

Observed

• run_all_tests_safe.sh stalls in-suite while child suite remains active under timeout.
• Example observed at test_edge_cases.sh under runner after tests started.
• Root pattern: host-wide sync calls in mounted-filesystem context.

Impact

Full 12-suite runner cannot finish consistently.

Proposed fix

• Replace sync in test suites with short bounded delays
• Keep process cleanup and isolation semantics
• Re-run full safe runner and verify stable completion