feat: add schedule builder API

[MilkBlock]

Summary

• add built-in RunSchedule / RunScheduleBuilder APIs and run_schedule helpers for rule runners
• preserve egglog repeat / saturate behavior, including early stop when no updates occur
• generate builder-based Rust for run-schedule when no :until clause requires the egglog bridge

Tests

• rustfmt --edition 2024 --check src/wrap/rule.rs src/prelude.rs eggplant-transpiler/src/eggplant.rs tests/schedule_builder.rs
• cargo test --test schedule_builder -- --nocapture
• cargo test -p eggplant-transpiler run_schedule -- --nocapture
• cargo test -p eggplant-transpiler eggcc_extraction -- --nocapture

[codspeed-hq]

Merging this PR will not alter performance

✅ 1 untouched benchmark
⏩ 2 skipped benchmarks¹

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_{Comparing codex/schedule-builder-stable (a885f4d) with stable (9a6d83e)}

Footnotes

1. 2 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. ↩