feat(maestro): optimistic session kill in sidebar

Close the kill dialog and remove the session card immediately on
confirm instead of waiting for the DELETE round-trip. Restores the
session if the daemon refuses with kill_guarded and re-opens the
dialog in force mode.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/components/sidebar/Sidebar.tsx

@@ -333,10 +333,25 @@ export function Sidebar(props: SidebarProps) {
           onCancel={() => setKill(null)}
           onConfirm={async () => {
             const { session: s, force } = kill;
+            // Close the dialog immediately and optimistically remove the
+            // session from the sidebar so the operator isn't staring at a
+            // spinner while the daemon tears down the tmux session.
+            setKill(null);
+            const store = props.store;
+            if (store) {
+              const next = new Map(store.getState().sessions);
+              next.delete(s.id);
+              store.setState({ sessions: next });
+            }
             try {
               await killSession(s.id, force);
-              setKill(null);
             } catch (e: unknown) {
+              // Restore the session so it reappears in the sidebar.
+              if (store) {
+                const restored = new Map(store.getState().sessions);
+                restored.set(s.id, s);
+                store.setState({ sessions: restored });
+              }
               // The daemon refuses an unforced kill over a worktree holding
               // unsaved work; that refusal needs its own prompt
               // (docs/WORKTREES.md).
@@ -349,7 +364,8 @@ export function Sidebar(props: SidebarProps) {
                 });
                 return;
               }
-              throw e;
+              // Nothing else we can usefully show — the session is back in
+              // the sidebar and the operator can retry.
             }
           }}
         />