test: avoid initial-break wait in restart-message

[inoway46]

Summary

Follow-up to #61773

test/parallel/test-debugger-restart-message.js can still flake on macOS unusual-path runs at the initial waitForInitialBreak(). This change syncs startup on Debugger attached. plus prompt.

failed CI log (main branch): https://github.com/nodejs/node/actions/runs/22545396955

Testing

UNUSUAL="$HOME/dir with \$unusual\"chars?'åß∂ƒ©∆¬…\`"
mkdir -p "$UNUSUAL"
ln -sfn "$PWD" "$UNUSUAL/node"
cd "$UNUSUAL/node"

• ./tools/test.py -p actions parallel/test-debugger-restart-message
• ./tools/test.py -p actions -j1 --repeat 40 parallel/test-debugger-restart-message
• CI passes on macOS

Refs: #61762

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.65%. Comparing base (4d0cb65) to head (3aa0054).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62060      +/-   ##
==========================================
- Coverage   91.63%   89.65%   -1.98%     
==========================================
  Files         337      676     +339     
  Lines      140376   206240   +65864     
  Branches    21768    39505   +17737     
==========================================
+ Hits       128627   184897   +56270     
- Misses      11527    13473    +1946     
- Partials      222     7870    +7648     

see 460 files with indirect coverage changes

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