Use packed arena tries for generic joins

[ezrosent]

Stacked on the packed-node and positioned-index abstractions PR.

This is the focused packed-executor integration:

• switch generic joins to arena-packed trie nodes
• use positioned indexes throughout join execution
• integrate packed cursors, constraints, and probing into the executor

The DVO policy is isolated below the abstraction layer, while demand-driven scheduling is isolated in the PR above this one.

Validation:

• cargo test -p egglog-core-relations
• cargo fmt --check
• cargo clippy -p egglog-core-relations --all-targets -- -D warnings

[codecov-commenter]

Codecov Report

❌ Patch coverage is 96.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 87.13%. Comparing base (80431f5) to head (3cfa98a).

Files with missing lines	Patch %	Lines
core-relations/src/free_join/frame_update.rs	83.33%	1 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##           codex/packed-join-abstractions     #959     +/-   ##
=================================================================
  Coverage                           87.13%   87.13%             
=================================================================
  Files                                  96       96             
  Lines                               31667    33023   +1356     
=================================================================
+ Hits                                27592    28775   +1183     
- Misses                               4075     4248    +173     

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[codspeed-hq]

Merging this PR will degrade performance by 7.82%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

❌ 3 regressed benchmarks
✅ 34 untouched benchmarks
⏩ 227 skipped benchmarks¹

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	tests[python_array_optimize]	1.2 s	1.3 s	-9.53%
❌	Simulation	tests[eggcc-2mm]	7.7 s	8.4 s	-7.65%
❌	Simulation	tests[typeinfer]	117.5 ms	125.3 ms	-6.24%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

---

_{Comparing ezr-better-parallel-packed-trie (3cfa98a) with codex/packed-join-abstractions (80431f5)}

Footnotes

1. 227 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. ↩