agent ui: input lives in terminal section, banner shimmer on activity

agent page restructure:
- send form moves into the terminal panel as a prompt-style row beneath
  the live tail (status line stays above so it still reads as a header).
- live panel + prompt share a single bordered 'terminal-wrap' box.
- harness-alive / login-state status lines drop their decorative ascii
  bookends; just a leading dot/glyph remains.
- banner gradient is now a real css gradient with a shimmer animation
  toggled by an .active class. turn_start adds it, turn_end removes it.
  dashboard side mirrors this: each broker sse event nudges a 4s
  shimmer window.
- dashboard container rows drop their static ▓█▓▒░ / ▒░▒░░ glyph
  prefixes; the role chips already disambiguate m1nd vs ag3nt.
- empty-state placeholders drop the ▓ bookends.

terminal pre-fill: hive-ag3nt::events::Bus grows a 500-event ring
buffer; new GET /events/history endpoint returns it. The agent JS
fetches history before opening the SSE stream so opening the page mid-
turn shows the last N events instead of a blank panel. The replay
walks turn_start/turn_end pairs to seed the banner-active state
correctly if a turn was still open.

hive-ag3nt/src/web_ui.rs

@@ -74,6 +74,7 @@ pub async fn serve(
         .route("/static/app.js", get(serve_app_js))
         .route("/api/state", get(api_state))
         .route("/events/stream", get(events_stream))
+        .route("/events/history", get(events_history))
         .route("/send", post(post_send))
         .route("/login/start", post(post_login_start))
         .route("/login/code", post(post_login_code))
@@ -206,6 +207,12 @@ async fn post_send(State(state): State<AppState>, Form(form): Form<SendForm>) ->
     }
 }
 
+async fn events_history(
+    State(state): State<AppState>,
+) -> axum::Json<Vec<crate::events::LiveEvent>> {
+    axum::Json(state.bus.history())
+}
+
 async fn events_stream(
     State(state): State<AppState>,
 ) -> Sse<impl Stream<Item = Result<Event, Infallible>>> {