Add user avatar management and moderation

docs/DESIGN_SYSTEM.md

@@ -187,3 +187,20 @@ follow.
 
 Repository agents and contributors should follow the maintenance checklist in
 `AGENTS.md`.
+
+### Agent avatars
+
+Agent portraits use a circular crop in identity headers and square tactical
+thumbnails in selectors. Preset choices appear in a compact four-column grid;
+the active choice uses the orange action border and an explicit pressed state.
+Custom images are normalized server-side to a metadata-free 256 × 256 WebP.
+Selectors must retain visible hover, focus-visible, pressed, pending, and
+disabled states, and collapse naturally with their containing account console.
+ISAC user dossiers show the current portrait, distinguish preset and custom
+sources textually, and place destructive custom-image removal behind the
+existing moderation permission and pending-action pattern.
+Moderation actions use full-width engineered controls: neutral outlined
+buttons for reversible identity changes and muted red controls for destructive
+or restrictive changes. Every control must expose pointer, hover,
+focus-visible, pressed, disabled, and inline pending-spinner states; adjacent
+navigation links use the same height, typography, and interaction motion.