• Support collecting and formatting web (V8 / Chrome) coverage reports in
  test_with_coverage via the new -p / --platform flag. Web runs delegate
  to dart test --coverage; VM runs continue to use the existing VM-service
  collection flow. Platforms other than vm and chrome are rejected, as are
  --function-coverage and --branch-coverage combined with a web platform,
  and platform flags passed through to the test script.
  Note that web coverage is measured on compiled JavaScript: code the compiler
  drops cannot be reported as uncovered, so line counts and percentages are not
  comparable to VM runs and --fail-under thresholds must be re-tuned per
  platform.
• Support scopeOutput filtering in HitMap.parseJsonSync, HitMap.parseJson,
  and HitMap.parseFiles, normalizing file: URIs inside known package library
  roots to package: URIs via Resolver.toPackageUri.
• test_with_coverage now fails immediately when the test process exits before
  the VM service is ready or before coverage collection finishes (for example,
  when the test path does not exist or fails to load) instead of waiting
  forever, and exits with the test process's exit code.
• HitMap.parseFiles now throws a FormatException when a file is not a valid
  {"coverage": [...]} report, instead of silently ignoring it, and
  parseChromeCoverage throws a FormatException when an entry is missing a
  string "scriptId".
• Migrate Dart subprocess spawning to package:cli_util (dartExecutable) to
  support AOT-compiled executables (dart compile exe / dart install).
• Resolver.resolve now rejects file: URIs that fall outside the known
  package/SDK roots or the current directory, instead of resolving them
  unconditionally.
• Fix a race condition in isolate teardown: ignore the benign errors
  produced when an isolate exits between its pause-on-exit callback
  completing and the resume request reaching the VM service.
• Also ignore SentinelException when resuming the main isolate after
  collection, matching the existing RPCError handling there.
• Require Dart 3.9.