test: reduce waitForInitialBreak() flakiness in debugger tests

[inoway46]

This fixes flakiness around waitForInitialBreak() in debugger tests.

waitForInitialBreak() can be flaky during startup because the CLI may already attach and print debug> before the initial break ... in output arrives. In some CI runs, tests end up waiting on that break message while startup output is still racing.

This change takes two approaches:

• Tests that do not depend on waitForInitialBreak() no longer use it.
• Tests that still need waitForInitialBreak() now wait for debug> first. This synchronizes with the CLI becoming interactive and reduces the startup race before waiting for the initial break.

CI failed logs on main branch (Nov 27, 2025 ~ Mar 8, 2026)

• test-debugger-help.mjs

  • https://github.com/nodejs/node/actions/runs/22783998746 (line 13)

• test-debugger-break.js

  • https://github.com/nodejs/node/actions/runs/22641591280 (line 17)

• test-debugger-preserve-breaks.js

  • https://github.com/nodejs/node/actions/runs/21915213108 (line 32)

• test-debugger-backtrace.js

  • https://github.com/nodejs/node/actions/runs/22250826545 (line 20)

• test-debugger-random-port-with-inspect-port.js

  • https://github.com/nodejs/node/actions/runs/21785139333 (line 16)

• test-debugger-watch-validation.js

  • https://github.com/nodejs/node/actions/runs/21772762644 (line 14)

• test-debugger-profile.js

  • https://github.com/nodejs/node/actions/runs/21589980783 (line 33)

• test-debugger-object-type-remote-object.js

  • https://github.com/nodejs/node/actions/runs/21568369570 (line 14)

• test-debugger-low-level.js

  • https://github.com/nodejs/node/actions/runs/21441860169 (line 17)

• test-debugger-exec.js

  • https://github.com/nodejs/node/actions/runs/21359022841 (line 15)

• test-debugger-set-context-line-number.mjs

  • https://github.com/nodejs/node/actions/runs/21336641272 (line 24)

• test-debugger-scripts.js

  • https://github.com/nodejs/node/actions/runs/20887752808 (line 18)

• test-debugger-sb-before-load.js

  • https://github.com/nodejs/node/actions/runs/22055336538 (line 23)

• test-debugger-exceptions.js

  • https://github.com/nodejs/node/actions/runs/22050359911 (line 20)

• test-debugger-clear-breakpoints.js

  • https://github.com/nodejs/node/actions/runs/22026231669 (line 23)

• test-debugger-auto-resume.mjs

  • https://github.com/nodejs/node/actions/runs/22474577256/attempts/1 (line 26)

Refs: #61762

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.65%. Comparing base (35d3bc8) to head (67c068f).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #61937      +/-   ##
==========================================
- Coverage   89.65%   89.65%   -0.01%     
==========================================
  Files         676      676              
  Lines      206231   206240       +9     
  Branches    39505    39510       +5     
==========================================
+ Hits       184898   184905       +7     
  Misses      13463    13463              
- Partials     7870     7872       +2     

see 34 files with indirect coverage changes

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