docs: note caption-banner review for existing casts in the handoff

Expand next-work item 2: review whether neutral step-caption banners (the demo
overlay) would improve the existing casts — narrating phases or calling out the
relationship diagram / teaching echo — cast-by-cast, with the no-naming-keys
constraint.

docs/handoff/20260611-website-handoff-2.md

@@ -130,8 +130,14 @@ output blocks** (capture-harness recipe below).
 
 ### 2. Consider a final cast re-record sweep + optional captions
 - All casts re-record with `pnpm casts` once the app is "final".
-- Optional: add neutral step **captions** (via the demo overlay) to specific
-  casts to label moments — text must not name keys (constraint above).
+- **Review whether caption banners would improve the existing casts.** The
+  demo overlay can show a neutral step **caption** (the stealth `Ctrl+]`
+  banner) to label or narrate a moment — e.g. marking the phases of the
+  build-the-library/projects casts, or calling out the relationship diagram /
+  the teaching echo in the modes cast. Go cast-by-cast and decide where a
+  caption adds clarity vs. adds noise. Constraint: caption **text must not name
+  keys** (no `j/k`, no `Ctrl+]`); it narrates *what* is happening, not *how* it
+  was typed. (Captions are wired but not yet used in any cast.)
 - Output-pane scrolling cast remains blocked (PgUp/PgDn unsendable). If desired
   later, it needs an app-side typeable scroll key (file an enhancement like #24)
   — otherwise leave it to static docs.