[WIP] Fix DF cast pushdown

[AdamGS]

Just putting a test here while I figure out the bigger question here.

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will degrade performance by 12.38%

_{Comparing adamg/issue-6211 (c5aa110) with develop (1dd2d66)}

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

Summary

⚡ 4 improved benchmarks
❌ 1 regressed benchmark
✅ 1174 untouched benchmarks
⏩ 1323 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	WallTime	10M_10pct[1000000]	251.3 µs	218.2 µs	+15.18%
⚡	WallTime	u64_FoR[10M]	388.1 µs	352.7 µs	+10.05%
❌	WallTime	10M_10pct[1000000]	218.6 µs	249.5 µs	-12.38%
⚡	WallTime	1M_50pct[500000]	57.1 µs	50.6 µs	+12.9%
⚡	WallTime	u8_FoR[10M]	39.3 µs	6.7 µs	×5.8

Footnotes

1. 1323 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩