init

static/js/state.js

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+/**
+ * static/js/state.js
+ * Centralised reactive state store.
+ * Components subscribe to state slices and are notified on change.
+ */
+
+const _state = {
+  instructions: [],   // InstructionItem[]
+  status: null,       // StatusResponse | null
+  config: null,       // ConfigResponse | null
+  serverOnline: false,
+};
+
+const _listeners = {};  // key -> Set<fn>
+
+export const state = {
+  get(key) {
+    return _state[key];
+  },
+
+  set(key, value) {
+    _state[key] = value;
+    (_listeners[key] || new Set()).forEach(fn => fn(value));
+  },
+
+  subscribe(key, fn) {
+    if (!_listeners[key]) _listeners[key] = new Set();
+    _listeners[key].add(fn);
+    // Immediately call with current value
+    fn(_state[key]);
+    return () => _listeners[key].delete(fn);   // unsubscribe
+  },
+};
+