debugger: wait for initial break output

[trivikr]

Fix a flaky test-debugger-run-after-quit-restart failure where the debugger
REPL could display debug> before the initial break output had been rendered.

The startup path now waits for the first local --inspect-brk pause render to
finish before completing REPL startup. Remote attach and
NODE_INSPECT_RESUME_ON_START=1 continue to skip that wait.

Refs:

• https://github.com/nodejs/node/actions/runs/27582782593/job/81546582775
• https://github.com/nodejs/node/actions/runs/27608332546/job/81625923848
• https://github.com/nodejs/node/actions/runs/27702868250/job/81943652942
• https://github.com/nodejs/node/actions/runs/27582782593/job/81546582775

Error Log

=== release test-debugger-run-after-quit-restart ===
Path: parallel/test-debugger-run-after-quit-restart
Error: --- stderr ---
/Users/runner/work/node/node/dir%20with $unusual"chars?'åß∂ƒ©∆¬…`/test/common/debugger.js:92
        const timeoutErr = new Error(`Timeout (${TIMEOUT}) while waiting for ${pattern}`);
                           ^

Error: Timeout (15000) while waiting for /break (?:on start )?in/i
    at /Users/runner/work/node/node/dir%20with $unusual"chars?'åß∂ƒ©∆¬…`/test/common/debugger.js:92:28
    at new Promise (<anonymous>)
    at Object.waitFor (/Users/runner/work/node/node/dir%20with $unusual"chars?'åß∂ƒ©∆¬…`/test/common/debugger.js:67:14)
    at Object.waitForInitialBreak (/Users/runner/work/node/node/dir%20with $unusual"chars?'åß∂ƒ©∆¬…`/test/common/debugger.js:116:18)
    at Object.<anonymous> (/Users/runner/work/node/node/dir%20with $unusual"chars?'åß∂ƒ©∆¬…`/test/parallel/test-debugger-run-after-quit-restart.js:18:7)
    at Module._compile (node:internal/modules/cjs/loader:1947:14)
    at Object..js (node:internal/modules/cjs/loader:2087:10)
    at Module.load (node:internal/modules/cjs/loader:1669:32)
    at Module._load (node:internal/modules/cjs/loader:1450:12)
    at wrapModuleLoad (node:internal/modules/cjs/loader:260:19) {
  output: '< Debugger listening on ws://127.0.0.1:62970/019e6944-4d82-44b5-956b-e4505af5b290\n' +
    '< For help, see: https://nodejs.org/learn/getting-started/debugging\n' +
    '< \n' +
    '\n' +
    '\n' +
    'connecting to 127.0.0.1:62970 ...\n' +
    '< Debugger attached.\n' +
    '< \n' +
    '\n' +
    ' ok\n' +
    '\n' +
    'debug> '
}

---

Assisted-by: openai:gpt-5.5

[trivikr]

Marked as draft as there are many CI to failures.