feat: add tab close menu actions (#24)

Co-authored-by: SuLe <sule@SuLedeMacBook-Air.local>

src/lib/tabCloseActions.ts

@@ -0,0 +1,26 @@
+export interface TabLike {
+  id: string;
+}
+
+export interface TabCloseState<T extends TabLike> {
+  tabs: T[];
+  activeTabId: string | null;
+}
+
+export function closeOtherTabsState<T extends TabLike>(
+  tabs: readonly T[],
+  activeTabId: string | null,
+  targetTabId: string,
+): TabCloseState<T> {
+  const target = tabs.find((tab) => tab.id === targetTabId);
+  if (!target) return { tabs: [...tabs], activeTabId };
+
+  return { tabs: [target], activeTabId: target.id };
+}
+
+export function closeAllTabsState<T extends TabLike>(
+  _tabs: readonly T[],
+  _activeTabId: string | null,
+): TabCloseState<T> {
+  return { tabs: [], activeTabId: null };
+}