Rewrite parser for openCypher 2024.3

[a-poor]

Summary

• Replace the Pest frontend with a lossless Logos lexer and generated LALRPOP parser.
• Add a public typed and spanned AST, structured diagnostics, strict parsing, and recovering parsing APIs.
• Target the pinned openCypher 2024.3 grammar and add an offline syntax projection of the upstream TCK.
• Add exact AST and span contracts, property tests, fuzz targets and seeds, Criterion benchmarks, coverage gates, and Rust 1.88 compatibility checks.
• Fix contextual-keyword parsing performance and correctness, including literal preservation and exact standalone YIELD spans.
• Harden checked-in parser generation with layout invariants and atomic replacement.

Verification

• Workspace tests pass with default and all features.
• Rust 1.88 workspace and independent fuzz workspace checks pass.
• Clippy passes for all targets and features with warnings denied.
• Rustdoc, formatting, benchmark compilation, expanded property tests, fuzz corpus replay, coverage, and local package verification pass.
• The openCypher release gate covers all 377 BNF productions and matches all 4,882 projected TCK occurrences with zero exclusions or open deviations.

Breaking changes

This is the planned 0.2 rewrite. It replaces the public Pest Rule and Pairs API with project-owned tokens, AST nodes, spans, and diagnostics. Migration guidance is included in docs/migration-from-0.1.md.

Known limitation

Label-heavy expression parsing still has nonlinear scaling. The benchmark suite now measures it from 4 through 64 KiB against a same-sized property-access control; this is tracked as performance debt rather than a correctness or merge blocker.