[ENH] Reduce complexity of run_flow_on_task func

[Omswastik-11]

Summary

This PR refactors run_flow_on_task, which had grown to ~160 lines with high cyclomatic complexity, by extracting small helper functions with clear, single responsibilities. The main function is now a readable orchestrator with clearly defined steps.

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Changes

Extracted helper functions

• _validate_flow_and_task_inputs
  Handles input validation and backward-compatible argument handling

• _sync_flow_with_server
  Synchronizes the flow with the server and checks for duplicate runs

• _prepare_run_environment
  Prepares environment information and run tags

• _create_run_from_results
  Builds the OpenMLRun object from execution results

Internal structure improvements

• Introduced a _RunResults NamedTuple to bundle execution outputs
  (data_content, trace, evaluations) and reduce long parameter lists

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Type Safety Improvements

• Replaced assert statements with explicit ValueError / TypeError exceptions
• Added type guards before accessing attributes that may be None
• Made boolean parameters keyword-only where appropriate

---

Fixes #1580

[codecov-commenter]

Codecov Report

❌ Patch coverage is 10.16949% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 52.01%. Comparing base (d421b9e) to head (cefae00).

Files with missing lines	Patch %	Lines
openml/runs/functions.py	10.16%	53 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1596      +/-   ##
==========================================
- Coverage   52.04%   52.01%   -0.04%     
==========================================
  Files          36       36              
  Lines        4333     4349      +16     
==========================================
+ Hits         2255     2262       +7     
- Misses       2078     2087       +9     

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[geetu040]

Looks really nice, I have left a few comments with only minor changes requested.

[Omswastik-11]

added cast(int , task_id) because of mypy pre-commit error .

[geetu040]

Nicely refactored, LGTM.

CC: @fkiraly, @SimonBlanke for review/merge.

[SimonBlanke]

@Omswastik-11 Do you see a way to increase the test coverage here? This is not a hard requirement.

[geetu040]

Actually there is no unit test for the function openml.runs.run_flow_on_task, could you please add one. There are some tests that use openml.runs.run_flow_on_task internally, but it would be nice to have an independent test that only checks this functionality. You can add this test in tests/test_runs.
Also if the helper functions in openml.runs.run_flow_on_task can be tested at unit (suggested in #1596 (review)), that would be nice, but again, it's not a hard requirement.