fix(test_scenario): stop apply_params_set writing NUM_NODES into cmd_args

[AmirF194]

Summary

TestRun.param_space (src/cloudai/_core/test_scenario.py) adds a "NUM_NODES" key to the
action space whenever num_nodes is a sweep list. apply_params_set then does two things
with that key: a generic per-key loop applies every action key to tdef.cmd_args via
setattr, and an explicit branch right after separately assigns it to new_tr.num_nodes.
Both fire on "NUM_NODES". Because CmdArgs is ConfigDict(extra="allow"), the generic
loop's setattr(tdef.cmd_args, "NUM_NODES", value) does not raise: it silently creates a
phantom NUM_NODES field on cmd_args that shows up in cmd_args.model_dump() and in any
persisted TestRunDetails dump, even though the workload itself never declared or accepted
that field. new_tr.num_nodes is still set correctly by the explicit branch, so the actual
job dispatch is unaffected, only the recorded/reported config is wrong.

Fix: skip "NUM_NODES" in the generic loop, since the explicit branch already owns it.

Test Plan

• tests/test_cloudaigym.py::test_params_set exercised every num_nodes sweep shape
  (1, [1, 2], [3]) already, but never asserted the field was absent from cmd_args.
  Added that assertion; confirmed it fails on main (AssertionError: 'NUM_NODES' in {...}) and passes with this change.
• uv run pytest (Python 3.14): full suite green except two pre-existing failures in
  tests/test_base_installer.py::TestPrepareOutputDir unrelated to this change (they assert
  a chmod-000 directory is unwritable, which does not hold when the test runs as root).
• uv run pytest -m ci_only, --dead-fixtures, and coverage report --include='tests/*' --fail-under=97.00 (98.92% here) all pass.
• uv run pre-commit run --files src/cloudai/_core/test_scenario.py tests/test_cloudaigym.py
  (pyright, ruff, vulture, import-linter, taplo) passes; controlled the same command on
  pristine main first to confirm a clean baseline.

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• src/cloudai/_core/test_scenario.py
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📝 Walkthrough

Walkthrough

The change keeps NUM_NODES outside command arguments and applies it to TestRun.num_nodes. A test verifies both behaviors.

Changes

NUM_NODES parameter handling

Layer / File(s)	Summary
Apply and validate NUM_NODES src/cloudai/_core/test_scenario.py, tests/test_cloudaigym.py	TestRun.apply_params_set skips command-argument assignment for NUM_NODES. The test confirms that the node count is updated without serializing NUM_NODES into command arguments.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Merge Risk: ⚪ Minimal · up to 5baee

This change prevents the internal NUM_NODES sweep parameter from being persisted as an unintended command argument while preserving node-count assignment; no actionable merge-blocking risk remains after normal checks and review.

Suggested reviewers: jj10306

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main fix: preventing NUM_NODES from being written into cmd_args.
Description check	✅ Passed	The description accurately explains the NUM_NODES defect, the fix, the test coverage, and validation results.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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