D248 — Backlink rewrite follows the graph

Decision. concept_move (and concept_merge) rewrites backlinks only in the concepts that can hold one: those the cached link graph (D241) says link to a moved id, those whose superseded_by names one (D243), and the moved concepts themselves (D160). Each is read once, at its physical path, in walk order. To make that exact, RewriteLinks resolves links exactly as ExtractLinks does: code spans are masked and an extensionless href naming an existing asset is not a concept (D150). RewriteOutboundLinks masks code spans too. This amends D72 (the rewrite scope is the inbound graph, not the whole KB) and aligns the rewrite with D150.

Why. A move read every concept, plus one index.md probe per concept: on the largest real KB that is 12 MB per move, to change a handful of pages. The graph already knows which pages link to the moved id. It could not be used because extraction and rewrite disagreed: a "link" inside a fenced block or inline code was rewritten by a move but never appeared in the graph. Aligning them costs a deliberate behaviour change: an example link inside code is no longer rewritten by a move, which is what D150 says it is — not a link.

Alternatives rejected. - Keep the full scan and only drop the per-concept probe: halves the cost, keeps it proportional to the KB instead of to the backlinks. - Keep rewriting inside code and add code-span links to the graph as a separate set: it would preserve an inconsistency D150 already ruled on, and keep a second link notion alive for one caller. - Rewrite via the adjacency without re-reading: the graph caches links, not bodies (D241); the body has to be read to be rewritten.

Consequences. Extraction and rewrite must resolve identically: both go through mdLinkTarget/wikiLinkTarget on the masked body, the trap is commented at both functions, and TestRewriteLinks_MatchesExtractLinks pins it as a property over generated bodies. TestRewriteBacklinks_MatchesFullScan keeps a full-scan oracle; TestWalkConceptsLinkingTo_ReadsOnlyCandidates proves a non-linking concept is not read, through an unexported readRawHook set only from export_test.go. A candidate that vanished between the graph validation and the read is skipped, as the walk skipped it.