test-runner: remove blocking sync between suites in run_all_tests_safe.sh

[T72]

Summary

tests/run_all_tests_safe.sh hangs between suites in WSL mode after completing suite 1.

Observed

• test_tm.sh completes and logs PASS.
• Runner then stalls with no child suite process active.
• Root cause: WSL safety block calls sync between suites, which can block indefinitely on mounted filesystems.

Impact

Cannot complete end-to-end 12-suite run even when individual suites pass.

Proposed fix

• Replace inter-suite sync with bounded non-blocking delay
• Keep cleanup and process-kill safety logic
• Re-run full suite for final confirmation

[T72]

Resolved by PR #92 (test(windows): stabilize shell suites and safe runner in WSL).