perf(tui): render streaming token secara inkremental + kurangi redraw sia-sia

- fix(view): token streaming kini benar-benar tampil — sebelumnya cache
  display_lines tidak pernah di-rebuild saat pesan terakhir berubah
  (msg_count == cached_count), jadi teks AI streaming tidak pernah muncul
  sampai pesan baru/resize
- perf(view): streaming kini hanya re-render pesan TERAKHIR (splice di
  batas cached_last_start) → O(konten baru) per token, bukan O(seluruh
  history); guard cached_last_len mencegah re-render pada frame spinner
  tanpa token baru
- perf(run): skip chrono::Utc::now() + drain toasts saat tidak ada toast
- perf(misc): drain_expired_toasts tidak lagi clone seluruh daftar toast
- perf(view): render_toasts fast-path saat toasts kosong

apps/interfaces/tui/src/state/misc.rs

@@ -179,16 +179,9 @@ impl MiscState {
         self.toasts.push(toast);
     }
 
-    /// Remove and return all toasts whose lifetime has expired at `now_ms`.
-    pub fn drain_expired_toasts(&mut self, now_ms: i64) -> Vec<Toast> {
-        let expired: Vec<_> = self
-            .toasts
-            .iter()
-            .filter(|t| t.expired(now_ms))
-            .cloned()
-            .collect();
+    /// Remove all toasts whose lifetime has expired at `now_ms`.
+    pub fn drain_expired_toasts(&mut self, now_ms: i64) {
         self.toasts.retain(|t| !t.expired(now_ms));
-        expired
     }
 }