test(p0): threshold-trace golden wiring + PVS scaffold + P1-entry checklist

P0 Tasks 6 (autonomous half) + 7. FindCellList_DoorwayThreshold_MatchesRetailTrace
asserts acdream's pick == each captured retail pick; skips until the capture
fixture lands. PvsConformanceTests scaffolds the render visible-set golden
(skipped; filled in P4). ConformanceDats.FixturesDir resolves fixtures from the
source tree (issue98 pattern). Notes record: existing retail traces are
collision-only (no membership) so the strict P1 gate needs the one live capture;
plus the P1 re-scope finding (Stage-1 membership already on this branch).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Tests/Conformance/Fixtures/README.md

@@ -0,0 +1,11 @@
+# Conformance fixtures
+
+Captured retail golden data for the P0 conformance tests.
+
+- `find-cell-list-threshold.log` — **pending capture.** Retail `find_cell_list` picks at the
+  Holtburg cottage doorway, in the `[fcl] seed=0x.. px=.. py=.. pz=.. picked=0x..` format read by
+  `RetailTrace.ParseFindCellList`. Produced by `tools/cdb/find-cell-list-capture.cdb` (see its
+  README). Until it lands, `FindCellList_DoorwayThreshold_MatchesRetailTrace` skips.
+
+Fixtures are read from this SOURCE directory (via `ConformanceDats.FixturesDir`), not copied to
+the build output — matching the existing `Fixtures/issue98/**` pattern.