docs: row 70 brief allows narrowing the pre-A2 fixture check

The first row 70 gate stopped at script-queue: dispatch.test.mjs requires
every pre-A2 fixture line, comments included, in scripts/mosaic, and the
fixture holds the header this row corrects.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/plans/2026-10-11_mosaic-on-path-docs.md

@@ -60,6 +60,12 @@ Owner: Sage. Reviewer: Filbert.
 - No code change. The cli, queue and seat node suites and every
   `scripts/test-*.sh` still pass. The queue dispatch test reads
   `scripts/mosaic`, and a header edit must not move its seat usage text.
+- Update, Sage 2026-10-15, after the first gate: the dispatch test's
+  "pre-A2 fixture" check requires every fixture line, comments included,
+  in `scripts/mosaic`, and the fixture holds the old "only reachable as
+  scripts/mosaic" header. This row may narrow that check to non-comment
+  lines, with mutants showing it still fails when a code line goes. No
+  other test or source change.
 
 ### Out of scope