D310 — A link to an expanded concept's index.md is the concept, normalised in the graph

Decision. The link graph stores a link target spelled <concept>/index under <concept> when that concept exists (buildGraphView); ExtractLinks and RewriteLinks are unchanged. A new info check index_link_form flags the spelling and kb_repair rewrites it: a markdown href to the relative <concept>.md (rebase_link), a wiki-link to the bare ID (rewrite_wiki_link, new). A broken_link that would resolve to the concept itself carries a rebase_link with an empty to, which drops the link and keeps the label.

Why. conceptFiles gives an expanded concept's index.md the ID of its directory, so map/c/index was never a node: backlinks missed the edge, orphan and cut_concept fired on a linked concept, reciprocal-link detection failed. D149 kept ExtractLinks literal so as not to break expanded_ambiguous, but that check stats files and never reads ExtractLinks, so the objection does not reach the graph. The real constraint is RewriteLinks, which must resolve as ExtractLinks does (D248) to rewrite the right href, so the normalisation sits one layer above, where edges are inserted.

Alternatives rejected. - Normalise inside ExtractLinks: would force the same in RewriteLinks, which needs the original href form to compute the new relative path. - Only the lint check, no graph change: leaves every graph tool wrong until each KB is repaired. - A new drop_self_link fix kind: an empty to on rebase_link stays inside the existing vocabulary. - Markdown to wiki-link rewriting in expanded indexes (the plan's first idea): needs label handling and a second fix kind; the relative <concept>.md is valid from the expanded base and is one mechanical rewrite.

Consequences. A target whose parent is no concept stays as written (a genuine broken link). checkCuratedIndex keeps its own CutSuffix("/index") because it reads raw ExtractLinks output. Graph topology changes for KBs that use the /index spelling: orphan and cut_concept findings may drop, index_link_form findings appear.