docs(lab): freeze M4.8 viewer and regression canon

docs/18_APPLICATION_COMPONENT_ARCHITECTURE.md

@@ -175,6 +175,36 @@ receives a concise typed projection.
 DOM or CSS classes. The product UI test discovers every `ENNResult.tsx`
 automatically and rejects such a fork.
 
+`components/laboratory/LaboratoryRecordedClipPlayer.tsx` exclusively owns the
+versioned `missioncore.laboratory-recorded-clip-viewer/v1` camera transport and
+clock. Feature renderers may add typed overlays or a synchronized spatial scene
+through its slots. Source-paced spatial evidence follows exact media sequences
+through a bounded reusable look-ahead cache; frame-step remains an explicit
+capability only when the source cannot keep pace. Experiment-named players must not fetch a JPEG
+per playback frame, instantiate MediaSource, schedule frame timers, or declare a
+new Rerun receiver/blueprint. Forward buffered progression and backward
+loop/seek are separate shared-player transitions; a backward target cannot be
+treated as an ordinary rolling-buffer advance.
+
+The shared player owns the admitted `primary` camera and `companion` camera +
+spatial presentations. A feature mode may not disable playback, unmount the
+camera, or create a second viewer configuration merely to show 3D/PLAN.
+`LaboratoryEvidenceViewer` owns the reusable `stacked` chrome layout: one header,
+one visual stage and one transport/timeline rail joined into a seamless surface.
+`LaboratoryRecordedClipPlayer` reuses the canonical `SplitPane` for resizable
+spatial + companion-camera evidence while keeping the recorded camera owner
+mounted across CAMERA/3D/PLAN transitions. Feature code supplies typed actions
+and modes; it does not declare a feature-local splitter. M4.8 reuses one
+`M48EvidenceModeRail` projection in the report, candidate-assisted correction,
+independent review and adjudication surfaces. The rail is the admitted
+viewport overlay: a canonical `GlassSurface` containing three default-size
+`IconButton` controls and no local control geometry. CAMERA/3D/PLAN therefore
+do not return to the stacked header or fork per workflow:
+CAMERA visibility is independent from the nullable 3D/PLAN spatial mode, and
+their state transition cannot hide both channels. Candidate seed data belongs
+to the correction contract only; it cannot enter the blind source decoder or
+upgrade assisted evidence to independent truth.
+
 Legacy/integrated diagnostic viewers may keep a result interaction inside the
 evidence slot only where that viewer is already the admitted result instrument.
 This exception does not apply automatically to a new LAB.