fix: Fix categorical value count sort panic regression

[bayoumi17m]

Overview

Fix panic when calling list operations (e.g., list.sort()) on lists containing structs with Categorical or Enum fields. This is a regression introduced in #25661 when we modified the operations to use try_apply_amortized_same_type.

Root Cause / Proposed fix

Root Cause

1. amortized_iter() converts structs to physical types, stripping _PL_CATEGORICAL2 metadata
2. try_apply_amortized_same_type tries to collect with the original dtype (which has metadata)
3. ListArray::new does strict dtype comparison including Arrow metadata → panic

Before #25661, try_apply_amortized inferred the dtype from collected values, and same_type() handled conversion afterward.

Proposed Fix

For list operations, check if inner type contains categoricals enums. If so, fall back to the more flexible try_apply_amortized + same_type approach that worked before #25661.

Originally, I did this in all list functions but extracted it to a helper that applies some closure F

Questions

1. Based on the code block below, it seems to imply that there may be more interesting behaviors if we try out dates or other types. Should we test those out? Or is this not relevant?

polars/crates/polars-core/src/chunked_array/list/iterator.rs

Lines 140 to 147 in e55c3b0

	let iter_dtype = match inner_dtype {
	#[cfg(feature = "dtype-struct")]
	DataType::Struct(_) => inner_dtype.to_physical(),
	// TODO: figure out how to deal with physical/logical distinction
	// physical primitives like time, date etc. work
	// physical nested need more
	_ => inner_dtype.clone(),
	};

AI Usage

1. I used AI over the past few weeks to understand the repository
2. I used AI to help understand all the PRs from 1.35.1 to 1.36.x to understand what changes are likely related to this issue

Fixes #26383

[codecov]

Codecov Report

❌ Patch coverage is 97.36842% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 81.00%. Comparing base (e55c3b0) to head (48a3cfe).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...tes/polars-core/src/chunked_array/list/iterator.rs	93.75%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #26412   +/-   ##
=======================================
  Coverage   80.99%   81.00%           
=======================================
  Files        1782     1782           
  Lines      243104   243138   +34     
  Branches     3078     3078           
=======================================
+ Hits       196901   196950   +49     
+ Misses      45400    45385   -15     
  Partials      803      803           

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