Warn when 'format' is used on a non-File parameter (#1616, #607)

[arimu1]

Summary

Fixes #1616 and #607.

format is only meaningful for File parameters. cwltool silently accepted it on Directory (and other) inputs/outputs, so --validate passed with no indication that the field would be ignored — exactly the "validation passes with no warnings/errors" behavior reported in #1616, and the "complains far too late" symptom in #607.

$ cwltool --validate format-on-directory.cwl
format-on-directory.cwl is valid CWL.    # before — no hint that `format` is bogus

Change

In Process.__init__ (cwltool/process.py), while iterating the tool's inputs/outputs, emit a warning when a parameter declares format but its type does not contain a File. A small recursive helper _type_contains_file handles plain (File), namespaced, array (File[]), nullable (File?) and record forms.

$ cwltool --validate format-on-directory.cwl
format-on-directory.cwl:10:5: 'format' is only valid for 'File' type parameters, but 'indir' is not a File; the 'format' field will be ignored.
format-on-directory.cwl is valid CWL.    # after

A warning (not a hard error as #607 literally suggested) was chosen so existing documents carrying a harmless stray format keep validating; this also matches the direction in the newer #1616. The warning respects --no-warnings/--quiet like other validation warnings.

Tests

Added tests/wf/format-on-directory.cwl and tests/wf/format-on-file.cwl fixtures, plus two tests in tests/test_validate.py:

• test_validate_warns_on_format_for_non_file — asserts the warning is emitted (captured via a custom log handler, as test_validate_custom_logger does).
• test_validate_no_format_warning_for_file — asserts format on a File does not warn.

I verified the warn-test fails against the pre-fix code and passes after, and that the File case never warns. Full test_validate.py passes (8); black/flake8/isort clean.

---

This change was produced with the assistance of Claude Code (model: Claude Opus). The diff, analysis, and tests were reviewed by a human before submission.