feat(gfql/cypher): execute WHERE NOT (pattern) via anti-semi row filtering (#1031 slice 2 phase 2b) - #1238

Closes #1235
Parent: #1031

Summary

• Execute WHERE NOT (pattern) by lowering negated WherePatternPredicate to a new row pre-filter call: anti_semi_apply
• Apply this lowering in both general MATCH lowering and connected OPTIONAL MATCH clause lowering
• Add row-pipeline runtime support for anti_semi_apply + call-safelist validation entry
• Preserve base-graph context on row-table transitions so correlated binding-ops evaluation can execute from row stages
• Add compile/runtime tests for NOT-pattern and mixed row+NOT behavior
• Amplify connected optional coverage with OPTIONAL MATCH ... WHERE NOT (pattern) tests (selective keep + null-fill fallback)

Key details

• Replaces the two lowering unsupported hooks for negated predicates with executable lowering
• Enforces per-predicate validation for negated patterns:
  • pattern must include a relationship
  • pattern cannot introduce new aliases
  • pattern must share at least one bound alias
• Emits row pre-filters via LoweredCypherMatch.row_pre_filters and runs them before row WHERE expressions

Validation

• UV_CACHE_DIR=/tmp/uv-cache PYTHONPATH=. uv run --no-project --with lark --with pytest python -m pytest graphistry/tests/compute/gfql/cypher/test_lowering.py -k "issue_1024_where_not_pattern_on_optional_match or negated_pattern or anti_semi" -q
• UV_CACHE_DIR=/tmp/uv-cache PYTHONPATH=. uv run --no-project --with lark --with pytest python -m pytest graphistry/tests/compute/gfql/cypher/test_lowering.py -q
• MYPY_CACHE_DIR=/tmp/mypy_cache ./bin/mypy.sh graphistry/compute/ast.py graphistry/compute/gfql/row/pipeline.py graphistry/compute/gfql/cypher/lowering.py graphistry/compute/gfql/call/validation.py

Follow-ups

• gfql/cypher: bound-aliases NOT-pattern + IC10 unblock (#1031 slice 2 phase 2c) #1237 (slice 2 phase 2c): bound-aliases NOT-pattern + IC10 unblock
• gfql/cypher: OR/XOR-around-pattern lowering via Apply/SemiApply runtime (#1031 slice 4) #1236 (slice 4): OR/XOR-around-pattern lowering