doc(createDeboucnedState): add JSDoc for createDebouncedState

src/shared/lib/helpers/createDebouncedState/createDebouncedState.svelte.ts

@@ -1,5 +1,28 @@
 import { debounce } from '$shared/lib/utils';
 
+/**
+ * Creates reactive state with immediate and debounced values.
+ *
+ * Useful for UI inputs that need instant feedback but debounced logic
+ * (e.g., search fields with API calls). The immediate value updates on
+ * every change for UI binding, while debounced updates after a delay.
+ *
+ * @param initialValue - Initial value for both immediate and debounced state
+ * @param wait - Delay in milliseconds before updating debounced value (default: 300)
+ * @returns Object with immediate/debounced getters, immediate setter, and reset method
+ *
+ * @example
+ * ```svelte
+ * <script lang="ts">
+ *   const search = createDebouncedState('', 300);
+ * </script>
+ *
+ * <input bind:value={search.immediate} />
+ *
+ * <p>Typing: {search.immediate}</p>
+ * <p>Searching: {search.debounced}</p>
+ * ```
+ */
 export function createDebouncedState<T>(initialValue: T, wait: number = 300) {
     let immediate = $state(initialValue);
     let debounced = $state(initialValue);
@@ -9,6 +32,7 @@ export function createDebouncedState<T>(initialValue: T, wait: number = 300) {
     }, wait);
 
     return {
+        /** Current value with immediate updates (for UI binding) */
         get immediate() {
             return immediate;
         },
@@ -17,9 +41,14 @@ export function createDebouncedState<T>(initialValue: T, wait: number = 300) {
             // Manually trigger the debounce on write
             updateDebounced(value);
         },
+        /** Current value with debounced updates (for logic/operations) */
         get debounced() {
             return debounced;
         },
+        /**
+         * Resets both values to initial or specified value.
+         * @param value - Optional value to reset to (defaults to initialValue)
+         */
         reset(value?: T) {
             const resetValue = value ?? initialValue;
             immediate = resetValue;