Spec p10-2 risks section calls out "거대 ConfigMap" but no test exercised
the line-window split branch of tier2_shared::push_chunks_with_oversize.
This adds a 256-line ConfigMap fixture (generated inline) and asserts:
- ≥2 chunks emitted (split happened),
- all chunks share symbol `ConfigMap/prod/big`,
- chunk_ids all distinct (id_for_chunk's #L{k} suffix disambiguation),
- line ranges form a contiguous partition (prev.line_end + 1 == next.line_start).
Reviewer nit #1 (PR #153 code-reviewer).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>