test: cover unsorted contiguous groups in one partition

[xavlee]

Which issue does this PR relate to?

• Part of Supporting analytics over large amounts of pre‑partitioned data #24438.

Rationale for this change

A source can concatenate sorted logical runs into one DataFusion output partition. The resulting rows can be globally unsorted while every distinct (key, time_bin) grouping tuple still occupies one contiguous range. This fixture records how aggregate planning handles that layout today.

What changes are included in this PR?

• Add a single-partition TestMemoryExec fixture containing two sorted logical runs whose (key, time_bin) order resets between runs.
• Group by the complete (key, time_bin) tuple.
• Assert InputOrderMode::Linear, EmissionType::Final, and the ordinary single-hash stream.

Stack

1. #24737 — test: cover unsorted contiguous groups in one partition ← this PR
2. #24697 — refactor: separate aggregate group completion from input ordering
3. #24698 — feat: add narrow group-contiguous source property
4. #24497 — feat: stream exact group-contiguous aggregates

Are these changes tested?

Yes, this PR itself only adds a test that serves to capture behavior today.

Are there any user-facing changes?

No.

Review this layer

View only this PR layer

[codecov-commenter]

Codecov Report

❌ Patch coverage is 76.31579% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.42%. Comparing base (ee59f62) to head (3b6d7ab).

Files with missing lines	Patch %	Lines
datafusion/physical-plan/src/aggregates/mod.rs	76.31%	2 Missing and 7 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #24737      +/-   ##
==========================================
- Coverage   81.42%   81.42%   -0.01%     
==========================================
  Files        1121     1121              
  Lines      402142   402180      +38     
  Branches   402142   402180      +38     
==========================================
+ Hits       327460   327488      +28     
  Misses      55484    55484              
- Partials    19198    19208      +10     

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