repl: reject --watch without script

[iclectic]

Fixes: #64135

This updates watch mode option validation so that node --watch without a script exits with an option error instead of falling through to the REPL.

Previously, the validation checked whether the argument list had fewer than one item. However, the argument list still contains the Node executable itself, so node --watch was not treated as missing a script. The check now requires at least two arguments, meaning the executable plus a script file.

A regression test has been added to confirm that node --watch:

• exits with code 9
• prints --watch requires specifying a file
• does not write to stdout

Tested with:

$ ./node --watch < /dev/null
./node: --watch requires specifying a file

$ ./node --test --test-name-pattern="require a file to watch" test/sequential/test-watch-mode-watch-flags.mjs
✔ should require a file to watch

[nodejs-github-bot]

Review requested:

• @nodejs/config

[MoLow]

LGTM

[aduh95]

Test failure: 'should watch changes to a file from config file'
Location: test/sequential/test-watch-mode.mjs:872:3
AssertionError [ERR_ASSERTION]: Expected values to be strictly equal:
+ actual - expected

+ '/Users/runner/work/node/node/node/out/Release/node: --watch requires specifying a file\n'
- ''

    at TestContext.<anonymous> (file:///Users/runner/work/node/node/node/test/sequential/test-watch-mode.mjs:881:12)
    at process.processTicksAndRejections (node:internal/process/task_queues:104:5)
    at async Test.run (node:internal/test_runner/test:1389:7)
    at async Suite.processPendingSubtests (node:internal/test_runner/test:960:7) {
  generatedMessage: true,
  code: 'ERR_ASSERTION',
  actual: '/Users/runner/work/node/node/node/out/Release/node: --watch requires specifying a file\n',
  expected: '',
  operator: 'strictEqual',
  diff: 'simple'
}