test_runner: restore directory search for --test

[bitpshr]

Fixes #64555. Passing a directory to node --test (like node --test tests) matched the directory itself as a glob pattern and then tried to run it as a test file, failing with MODULE_NOT_FOUND.

This expands a pattern that resolves to a directory into a search for the default test files inside it, restoring the pre-glob behavior. File paths, real glob patterns, and nonexistent arguments all pass through unchanged.

Note: This isn't Windows-specific despite the report; it reproduces on every platform (on macOS, node@20 searches the directory and passes while node@22 and node@24 both fail).

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[bitpshr]

Both CI failures look unrelated to this change. test-macOS failed on test-debugger-probe-script-throws.js in the "unusual chars folder" re-run step, and the aarch64 shared-boringssl build failed on test-repl-context.mjs with ERR_INSPECTOR_COMMAND: Inspector error -32000: Promise was collected (the log shows failed 1 out of 10, so it's flaky). This PR only touches test runner directory handling, and its own test passed. A re-run should clear them.

[bitpshr]

Just keeping this on the radar. It's been approved for a couple of weeks now, and it's a small test_runner fix (restoring directory arguments to node --test) with a regression test. @MoLow is there anything else needed to get it landed?

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.13%. Comparing base (6071907) to head (b48ff5b).
⚠️ Report is 262 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #64637   +/-   ##
=======================================
  Coverage   90.13%   90.13%           
=======================================
  Files         741      741           
  Lines      242076   242095   +19     
  Branches    45550    45552    +2     
=======================================
+ Hits       218199   218219   +20     
+ Misses      15391    15386    -5     
- Partials     8486     8490    +4     

Files with missing lines	Coverage Δ
lib/internal/test_runner/runner.js	94.52% <100.00%> (+0.09%)	⬆️

... and 24 files with indirect coverage changes

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[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/75590/