align_sections_to_v4_granularity now emits canonical sub-section ids
of the form ${section_id}-sub-${ordinal} (e.g., "04-2-sub-1"), matching
the frontend drag/drop schema. Each drilled sub-section populates
heading_number (decimal "2.1" / integer "1" / None for undecorated)
and v4_alias_keys for legacy V4 keys.
N-R5 decimal-only alias guard : v4_alias_keys is populated only when
heading_number matches re.fullmatch(r"\d+\.\d+", ...). Integer-only
H3 headings (e.g., MDX 05's "### 1", "### 2") and bare H3 headings
produce no alias to avoid sibling-parent V4 collisions (RULE 0
generalization — applies to all 32-frame MDX, not MDX 05-specific).
The drill regex is broadened from r"^###\s+(\d+\.\d+)\s+..." to
r"^###\s+(?:(\d+(?:\.\d+)?)\s+)?(.+?)$" so integer-only and bare H3
headings are now recognised as sub-sections; they previously failed
the regex and were silently kept under the parent section.
Tests : 7 new cases (MdxSection default 4-positional callers, V4 exact
passthrough, decimal drill with alias, integer-only no-alias guard,
bare H3 no-alias, no-H3 passthrough, end-to-end aligner -> resolver
round-trip with legacy V4 alias). 15/15 in test_phase_z2_subsection_schema
+ 14 override + 8 fallback baseline = 37/37 PASS.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
kyeongmin
5191acad85