Source-span citations, not file-level links

Layer: ingestion / provenance.

Claims should point at the exact passage they rest on, not at a whole source file. This is already the first queued experiment in epistack-competition ("does file-level linking suffice, or do claims need a source-span locator type?"). ADR 023 already built quote-anchored citations for code-grounded reviews — the precedent to generalize into a claim → source-span locator, so a claim points at the exact passage it rests on and review can verify the quote still says what the claim says.

Prototype this and the dialectical/evidential register first — everything else hangs off those two.