asdf

Squash the current repository state back into one baseline commit while
preserving the README reframing and repository contents.

Constraint: User explicitly requested a single squashed commit with subject "asdf"
Confidence: high
Scope-risk: broad
Reversibility: clean
Directive: This commit intentionally rewrites published history; coordinate before future force-pushes
Tested: git status clean; local history rewritten to one commit; force-pushed main to origin and instructkr
Not-tested: Fresh clone verification after push

src/utils/signal.ts

@@ -0,0 +1,43 @@
+/**
+ * Tiny listener-set primitive for pure event signals (no stored state).
+ *
+ * Collapses the ~8-line `const listeners = new Set(); function subscribe(){…};
+ * function notify(){for(const l of listeners) l()}` boilerplate that was
+ * duplicated ~15× across the codebase into a one-liner.
+ *
+ * Distinct from a store (AppState, createStore) — there is no snapshot, no
+ * getState. Use this when subscribers only need to know "something happened",
+ * optionally with event args, not "what is the current value".
+ *
+ * Usage:
+ *   const changed = createSignal<[SettingSource]>()
+ *   export const subscribe = changed.subscribe
+ *   // later: changed.emit('userSettings')
+ */
+
+export type Signal<Args extends unknown[] = []> = {
+  /** Subscribe a listener. Returns an unsubscribe function. */
+  subscribe: (listener: (...args: Args) => void) => () => void
+  /** Call all subscribed listeners with the given arguments. */
+  emit: (...args: Args) => void
+  /** Remove all listeners. Useful in dispose/reset paths. */
+  clear: () => void
+}
+
+export function createSignal<Args extends unknown[] = []>(): Signal<Args> {
+  const listeners = new Set<(...args: Args) => void>()
+  return {
+    subscribe(listener) {
+      listeners.add(listener)
+      return () => {
+        listeners.delete(listener)
+      }
+    },
+    emit(...args) {
+      for (const listener of listeners) listener(...args)
+    },
+    clear() {
+      listeners.clear()
+    },
+  }
+}