fix(graph): correct Cypher NOT precedence

[ruvnet]

Outcome

Cypher NOT now binds looser than comparison and tighter than AND. Queries such as NOT n.age = 30 produce NOT (n.age = 30) instead of (NOT n.age) = 30.

Invariants

1. Comparison expressions remain inside NOT.

2. NOT expressions remain inside AND.

3. Arithmetic unary minus retains its existing precedence.

Validation

cargo test -p ruvector-graph passed 352 tests with 13 existing ignored tests.

cargo clippy -p ruvector-graph --all-targets -- -D warnings passed.

RuFlo diff risk reported low risk with score 0 of 100.

Risk

The intentional behavior change affects AST shape for unparenthesized NOT expressions. Exact AST regression tests lock the Cypher precedence contract.

Fixes #939

[ruvnet]

Post-merge Dream review for exact head df644e2a4050901fe8b75db9d2c512255b854f78.

The parser change matches the current Neo4j Cypher boolean precedence: comparisons bind before NOT, which binds before AND. Focused validation reports 352 graph tests passing with 13 existing ignores, clippy passes, and exact-head graph-native, regression, supply-chain, fmt/clippy, and WASM-dedup workflows are green.

Portfolio verdict: INCONCLUSIVE rather than ACCEPT because required Workspace CI run 33321172176 cancelled its core-and-rest shard. The narrow AST semantics are supported; repository-wide promotion remains blocked until that shard completes on the exact candidate or merge head.