Closes#2301
## Root cause
graphify's JSON output uses the key `links` for edges, but graphify.cjs
reads `graph.edges` at four sites (buildAdjacencyMap, status edge_count,
diff currentEdgeMap/snapshotEdgeMap, snapshot writer). Any graph produced
by graphify itself therefore reported edge_count: 0 and adjacency maps
with no entries.
## Fix
Added `|| graph.links` fallback at all four read sites so both key names
are accepted. The snapshot writer now also normalises to `edges` when
saving, ensuring round-trips through the snapshot path use a consistent key.
## Test
Added LINKS-01/02/03 regression tests covering buildAdjacencyMap,
graphifyStatus edge_count, and graphifyDiff edge change detection with
links-keyed input graphs.
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
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