[codex] Add eggcc proof baseline helpers

[saulshanabrook]

Summary

Refreshes the eggcc proof baseline onto a new egglog core branch made from current egglog main merged with egglog PR #927:

• egraphs-good/egglog, branch codex/pr927-main-exp56-refresh
• locked at d69df09a74800b68a727b2c39b1e5cca31042b3e
• merge inputs: main 7e926c6e2842db66c3f40e5cb6139a6406a9d05a + PR #927 9a37d278337f0b557a3d27fd4b7a729a8a1bf2d2

Changes in this PR:

• Point egglog, egglog-ast, and egglog-reports at the refreshed core branch.
• Port keep-best, print-table-stats, and dynamic set-cost extraction from the removed FunctionRow / function_for_each / lookup_function / with_full_state APIs to the current function_entries, constructor_enodes, read, and update APIs.
• Preserve support for constructor/relation tables in keep-best and print-table-stats by falling back from function-entry scans/writes to constructor enode scans/adds.
• Keep the checked-in eggcc 2mm pass-1 export at tests/fixtures/eggcc-2mm-pass1-merge-old.egg with former :no-merge functions represented as :merge old.

Validation

Core, in /Users/saul/p/wt/egg-smol/pr927-main-exp56-refresh:

cargo check -p egglog --release

Experimental, in /Users/saul/p/wt/egglog-experimental/eggcc-proof-baseline-pr927-refresh-worker:

cargo check --release --lib
cargo build --release --bin egglog-experimental
cargo test --release --test integration_test
cargo test --release --test eggcc_2mm_proof
git diff --check

Results: all commands passed. integration_test passed 39/39. eggcc_2mm_proof passed the checked-in fixture/static test; the full proof canary remains ignored in the test harness.

Release Timings

Timed in /Users/saul/p/wt/egglog-experimental/eggcc-proof-baseline-pr927-refresh-worker with the release binary and the checked-in fixture.

Mode	Command	Exit	Wall time	Max RSS	Notes
no proofs	/usr/bin/time -l target/release/egglog-experimental tests/fixtures/eggcc-2mm-pass1-merge-old.egg	0	1.44s	117,932,032 bytes	Emits only the expected global-name warning.
proofs	/usr/bin/time -l target/release/egglog-experimental --proofs tests/fixtures/eggcc-2mm-pass1-merge-old.egg	0	17.76s	3,543,302,144 bytes	Runs proof mode successfully. The fixture has no explicit (check ...) or (prove ...) forms, so this exercises proof-mode instrumentation/generation but does not print a proof-testing result. It emits proof-normal-form warnings for non-top-level function calls in query facts.

Downstream users can depend on the refreshed core branch with:

egglog = { git = "https://github.com/egraphs-good/egglog.git", branch = "codex/pr927-main-exp56-refresh", default-features = false }
egglog-ast = { git = "https://github.com/egraphs-good/egglog.git", branch = "codex/pr927-main-exp56-refresh", default-features = false }
egglog-reports = { git = "https://github.com/egraphs-good/egglog.git", branch = "codex/pr927-main-exp56-refresh", default-features = false }

[saulshanabrook]

Closing in favor of saulshanabrook/egglog-encoding#8 for now