Summary

• replace waitForInitialBreak() with attach/prompt synchronization in:
  • test/parallel/test-debugger-watch-validation.js
  • test/parallel/test-debugger-extract-function-name.mjs
  • test/parallel/test-debugger-random-port-with-inspect-port.js
• for tests that do not assert initial break ... in output, sync on Debugger attached. (+ waitForPrompt() where needed)
• keep test/common/debugger.js behavior unchanged (test-side synchronization only)

Context

test-macOS unusual-path failures have shown intermittent timeouts in waitForInitialBreak() for attach-only debugger tests.
In failing logs, attach and prompt can appear, but the initial break banner wait becomes a fragile sync point.

• test/parallel/test-debugger-watch-validation.js
  • failed CI log: https://github.com/nodejs/node/actions/runs/21772762644/job/62823422649
• test/parallel/test-debugger-extract-function-name.mjs
  • failed CI log: https://github.com/nodejs/node/actions/runs/22266947520
• test/parallel/test-debugger-random-port-with-inspect-port.js
  • failed CI log: https://github.com/nodejs/node/actions/runs/21785139333/job/62855280668

Hypothesis

The flake is likely a timing race in startup output ordering:

• waitForInitialBreak() depends on observing the initial break ... in banner
• under some timing conditions, attach/prompt ordering differs and the break-banner wait becomes brittle for tests that do not actually assert break-banner content

This change narrows synchronization only in the three target tests and does not claim a single root cause in debugger internals.

Why this approach

• keep test intent intact
• reduce dependence on a brittle initial-break wait for attach-only assertions
• minimize blast radius by changing only affected tests

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-watch-validation (passes locally)
• ./tools/test.py -p actions parallel/test-debugger-random-port-with-inspect-port (passes locally)
• ./tools/test.py -p actions parallel/test-debugger-extract-function-name (passes locally)
• Additional unusual-path stress runs were executed on this PR branch:
  • ./tools/test.py -p actions -j1 --repeat 50 parallel/test-debugger-watch-validation parallel/test-debugger-random-port-with-inspect-port parallel/test-debugger-extract-function-name
  • ./tools/test.py -p actions -j4 --repeat 100 parallel/test-debugger-watch-validation parallel/test-debugger-random-port-with-inspect-port parallel/test-debugger-extract-function-name
• CI passes on macOS

Refs: #61762