feat(models): render blueprint vars in columns dict

[lafirm]

Description

This PR fixes issue #5767 - adds support for rendering Python model columns keys (column names) and values (column types) from blueprint/global variables. Previously, column names were not rendered.

Problem

Python model metadata rendering supported macro expansion for many fields, but columns had gaps:

• Column names in columns={...} could not be parameterized (for example, @{col_name})
• Column types parameterized via macros/blueprints needed to render correctly before model creation
• Existing early validation expectations for plain string column types (no macro syntax) needed to remain intact

This made blueprint-driven Python models less flexible and caused dialect validation edge cases.

What Changed

1. Added explicit rendering logic for the columns field so both:
   • column names are rendered (keys)
   • column types are rendered (values), including macro/blueprint expressions
2. Updated Python model decorator behaviour to:
   • preserve columns in kwargs for later render-time handling
   • validate non-macro plain string column types early
   • defer macro-containing column type validation until after rendering
3. Ensured rendered columns are used when constructing the Python model

Test Plan

1. Added coverage for blueprint-based dynamic column names and types in Python models
2. Added coverage for global-variable-based dynamic column names
3. Kept/validated existing dialect behaviour around invalid non-macro column type parsing
4. Included formatting-only updates from ruff in a few unrelated files (no behaviour changes)

Docs

Updated Python model blueprinting docs with an example showing blueprint variables used for:

1. column names
2. column types

Validation

Ran targeted tests successfully:

1. python3 -m pytest tests/core/test_model.py::test_python_model_dialect -x -q
2. python3 -m pytest tests/core/test_model.py::test_python_model_blueprint_column_names tests/core/test_model.py::test_python_model_variable_column_names -x -q
3. python3 -m pytest tests/core/test_model.py -k "blueprint" -q
4. python3 -m pytest tests/core/test_model.py::test_python_model_dialect tests/core/test_model.py -k "column" -q

Backward Compatibility

1. Existing static columns definitions continue to work unchanged.
2. Invalid plain string column types still fail early (same expectation as before).
3. Macro/blueprint-driven columns now work as intended.

Checklist

• I have run make style and fixed any issues
• I have added tests for my changes (if applicable)
• All existing tests pass (make fast-test)
• My commits are signed off (git commit -s) per the DCO

Reviewer Notes

1. Core behaviour is in Python model metadata rendering and decorator preprocessing
2. A few additional files were touched by ruff formatting only; they do not introduce functional changes