debugger: wait for target startup

[panva]

Important

This ought to deflake parallel/test-debugger-profile

The inspector can accept a connection before an --inspect-brk target enters its frontend wait. Runtime.runIfWaitingForDebugger can then be handled too early, allowing the target to subsequently block forever.

Wait for NodeRuntime.waitingForDebugger before initializing and releasing launched targets. Race the handshake against disconnects and apply it to both interactive and probe startup.

Refs: #64116
Assisted-by: codex:gpt-5.6-sol

[panva]

The startup-readiness handshake and its initial integration were adapted from @Archkon's work in #64304. This version narrows and hardens that approach by covering disconnects during the full handshake, preserving probe-mode structured errors, and adding focused failure and cleanup tests.

[codecov]

Codecov Report

❌ Patch coverage is 91.04478% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.32%. Comparing base (404b0cf) to head (821e267).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/internal/debugger/inspect_probe.js	50.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #65194      +/-   ##
==========================================
- Coverage   90.32%   90.32%   -0.01%     
==========================================
  Files         760      760              
  Lines      248525   248590      +65     
  Branches    46894    46909      +15     
==========================================
+ Hits       224488   224534      +46     
- Misses      15469    15472       +3     
- Partials     8568     8584      +16     

Files with missing lines	Coverage Δ
lib/internal/debugger/inspect_helpers.js	97.92% <100.00%> (+0.51%)	⬆️
lib/internal/debugger/inspect_repl.js	91.34% <100.00%> (+0.03%)	⬆️
lib/internal/debugger/inspect_probe.js	81.60% <50.00%> (-0.45%)	⬇️

... and 29 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75746/