feat: implement persistent terminal sessions

- Terminal sessions now persist across WebSocket disconnections
- Added circular output buffer (10KB) for replay on reconnect
- Added idle timeout cleanup (30 minutes)
- Added reset functionality via WebSocket message and HTTP endpoint
- Concurrent connections close old WebSocket when new one connects
- Frontend: Added reset button with confirmation dialog
- Frontend: Handle resetting status and reconnection

Refs: persistent-terminal-sessions

apps/web/src/styles.css

@@ -3388,6 +3388,57 @@ a.nav-item,
   font-size: 0.75rem;
 }
 
+.terminal-reset-confirm {
+  position: absolute;
+  top: 0;
+  left: 0;
+  right: 0;
+  bottom: 0;
+  background: rgba(0, 0, 0, 0.8);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 100;
+}
+
+.terminal-reset-confirm-content {
+  background: var(--bg-surface);
+  border: 1px solid var(--border-color);
+  border-radius: 8px;
+  padding: var(--space-4);
+  max-width: 400px;
+  text-align: center;
+}
+
+.terminal-reset-confirm-content p {
+  margin: 0 0 var(--space-4) 0;
+  color: var(--text-primary);
+}
+
+.terminal-reset-confirm-buttons {
+  display: flex;
+  gap: var(--space-2);
+  justify-content: center;
+}
+
+.terminal-reset-confirm-button {
+  padding: var(--space-2) var(--space-4);
+  border: none;
+  border-radius: 4px;
+  cursor: pointer;
+  font-size: 0.875rem;
+}
+
+.terminal-reset-confirm-button.cancel {
+  background: var(--bg-elevated);
+  color: var(--text-primary);
+}
+
+.terminal-reset-confirm-button.confirm {
+  background: #cd3131;
+  color: white;
+}
+
 .terminal-hidden-input {
   position: fixed;
   left: -9999px;