test(ci): [CI-01] checkpoint installed adaptive and thumbnail coverage

packages/artplayer-plugin-auto-thumbnail/ARCHITECTURE.md

@@ -227,3 +227,15 @@ The internal type checkpoint and its core-host assignment fixture are recorded i
 `refactor/changes/2026-09-13-PKG-AUTO-THUMB-03-internal-types.md`. A core host can
 hold partial user thumbnail options; extraction publishes a complete sheet. Do not
 require the host's existing getter to have every generated-sheet field.
+
+## Shared installed browser scope
+
+autoThumbnailCandidate reads verified installed bytes through browser-candidate.js. Native video/JPEG lifecycle and pixel files retain their stub player host and exact presentation-callback/fallback limits. The historical file still loads its frozen old artifacts. Installed mode rejects frozen-workspace and explicit-artifact overrides. These are native extraction checks, not full core integration or first-frame acceptance on every engine.
+
+Use the exact twelve-package preparation command and scope rules in
+../../scripts/browser-validation/README.md. Missing, stale or changed installation
+inputs fail without source fallback. Attachments distinguish selected installed,
+source and published inputs. Source mode retains existing explicit artifact use.
+The generic Node/type consumer remains core/chapter-only. Module forms, physical
+devices, editor demos and release readiness retain their separate package gates.
+See ../../refactor/changes/2026-09-15-CI-01-adaptive-installed.md for actual results.