Pure bidirectional-link engine for the sticky-note/board system (a user-named
differentiator). parseLinkTargets extracts trimmed, de-duped [[targets]];
LinkGraph builds forward + backlink indices (fromTexts parses, fromLinks takes
explicit targets), ignores self-links, and danglingTargets() surfaces links to
unknown nodes. Widget-free + storage-free so it is fully unit-tested; the board
UI + persistence wrap it later.
Built ahead of its phase deliberately as a zero-rework-risk pure data structure
(not rendering/perf — the P0.5 device gate can't invalidate it).
flutter analyze lib/editor clean; 139/139 tests (+10: parsing, backlinks,
self-link, dangling, immutability).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
