perf: canonicalize internal equality assertions

[1sgtpepper]

Description

Canonicalize internal-variable equality assertions so equivalent wires share a representative instead of emitting an extra a - b == 0 constraint.

This reduces the issue #555 equality-heavy case by removing redundant equality constraints and internal wires where aliasing is valid.

Fixes #555

Type of change

• Optimization / performance improvement

How has this been tested?

• Added unit, frontend builder, and issue reduce constraint generated with api.AssertIsEqual(...) #555 regression coverage.
• Refreshed affected stats fixtures.
• Fork Actions issue555-proof: changed-surface tests and benchmark passed.
• Fork Actions issue555-full-proof: upstream short test block passed.
• Fork Actions pull_request/staticcheck: gofmt, goimports, generated-file check, and golangci-lint passed.

How has this been benchmarked?

• go test ./internal/regression_tests/issue555 -run '^$' -bench BenchmarkInternalEqualityCanonicalizationCompile -benchtime=100x -count=3

Benchmark result: R1CS and SCS equality-heavy paths match the baseline at 2048 constraints/op and 2048 internal_variables/op; aliasing adds one instruction.

Checklist:

• I have performed a self-review of my code
• I have added tests that prove my fix is effective or that my feature works
• I did not modify files generated from templates
• golangci-lint does not output errors locally
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

---

Note

High Risk
Changes compile-time constraint generation and post-compile wire rewriting/solving across R1CS and SCS; incorrect alias eligibility could weaken soundness, though extensive regression tests target escape cases.

Overview
R1CS and SCS builders now track safe internal-wire equalities with a union-find wirealias.Set instead of always emitting a - b == 0. AssertIsEqual on two pure unit terms calls Union and skips the constraint when aliasing is allowed; witness/public/secret equalities and wires that escape (hints, commitments, custom instructions, ToCanonicalVariable, etc.) stay explicitly constrained via MarkNoAlias / MarkInternal.

At compile, applyWireAliases rewrites constraint calldata to canonical wire IDs and appends a BlueprintWireAliases solver instruction so eliminated wires copy their representative’s value. System.ApplyWireAliases rebuilds the instruction tree and resets lookup-hint level caches when aliases change.

Constraint layer adds BlueprintWireAliases, marshaling registration, and tests for serialization, lookup-hint rewrite, and level-cache reset.

Tests and stats: issue #555 regression suite, builder/unit tests, and updated Plonk constraint counts in latest_stats.csv where redundant equalities dropped.

^{Reviewed by Cursor Bugbot for commit c458205. Bugbot is set up for automated code reviews on this repo. Configure here.}