Two fixes from Ganymede review:
1. CRITICAL: blank line before closing --- compounded on repeat reweaves.
Body starts with \n---, so \n{body} created \n\n---. Fixed by checking
body prefix.
2. Replaced yaml.dump round-trip with _serialize_edge_fields() that splices
only edge arrays into raw frontmatter text. Non-edge fields (title,
confidence, type, quotes, flow styles) stay byte-identical to main HEAD.
_parse_yaml_frontmatter now returns 3-tuple: (dict, raw_fm_text, body).
_serialize_frontmatter takes (raw_fm_text, merged_edges_dict, body).
26 tests pass including idempotency (5x serialize), formatting preservation,
and no-blank-line regression test.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
m3taversal
b091642146