Add 34 comprehensive tests (50 total) covering point-to-point, E2E, edge cases, aspects, and ABI

Tests added across 5 categories:
- Point-to-point: each pattern (loop-sum, map-transform, filter-predicate, sort, group-by) generates correct BQN primitives
- End-to-end: full pipeline from manifest to .bqn/FFI files, nested dirs, spaces in names
- Edge cases: empty patterns, duplicate names, invalid types, missing fields, nonexistent files, defaults
- Aspect: SPDX headers, C-ABI declarations, Zig FFI structure, Unicode correctness, assignment arrows
- ABI: glyph uniqueness, label/arity validation, exhaustive mapping, field preservation, Display traits

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hyperpolymath