refactor: simplify array optimizer

[connortsui20]

Summary

Cleans up optimizer fixpoint and session parent-reduce dispatch without changing rule order or behavior.

Changes

Names the iteration limit and moves session-kernel dispatch into a focused helper. Session kernels still run before static parent rules and in registration order.

[codspeed-hq]

Merging this PR will improve performance by 12.51%

⚠️ Unknown Walltime execution environment detected

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

⚡ 5 improved benchmarks
✅ 2107 untouched benchmarks
⏩ 106 skipped benchmarks¹
🗄️ 4 archived benchmarks run²

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	take[duplicates/repeated/primitive/nonnull/chunks=16/indices=1000]	245 µs	206.9 µs	+18.44%
⚡	Simulation	compact[(2048, 90)]	1.5 µs	1.4 µs	+11.89%
⚡	WallTime	mul_u32_nonnull_avx512	6.3 µs	5.6 µs	+11.54%
⚡	Simulation	compress_fsst[(500, 64, 4)]	488.1 µs	441.7 µs	+10.5%
⚡	Simulation	compress_fsst[(500, 64, 8)]	524.9 µs	475.5 µs	+10.39%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing ct/array-optimizer-cleanup (ca662e7) with develop (ee1ac25)}

Footnotes

1. 106 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. ↩

2. 4 benchmarks were run, but are now archived. If they were deleted in another branch, consider rebasing to remove them from the report. Instead if they were added back, click here to restore them. ↩