Clarify requestLimitedSnapshot comments

Remove confusing "index exhausted" terminology and clarify that this
function loads from local collection via BTree index and also triggers
async backend fetch.

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: KyleAMathews

packages/db/src/collection/subscription.ts

@@ -400,19 +400,22 @@ export class CollectionSubscription
   }
 
   /**
-   * Sends a snapshot that fulfills the `where` clause and all rows are bigger or equal to the cursor.
-   * Requires a range index to be set with `setOrderByIndex` prior to calling this method.
-   * It uses that range index to load the items in the order of the index.
+   * Loads rows from the local collection in sorted order using the BTree index.
+   *
+   * Uses the BTree index (set via `setOrderByIndex`) to iterate through the local
+   * collection's data in sorted order, starting from the cursor position (`minValues`).
+   * Also triggers an async `loadSubset` call to fetch more data from the sync layer
+   * (e.g., Electric backend) if needed.
    *
    * For multi-column orderBy:
-   * - Uses first value from `minValues` for LOCAL index operations (wide bounds, ensures no missed rows)
-   * - Uses all `minValues` to build a precise composite cursor for SYNC layer loadSubset
+   * - Uses first value from `minValues` for BTree index operations (wide bounds, ensures no missed rows)
+   * - Uses all `minValues` to build a precise composite cursor for sync layer loadSubset
    *
-   * Note 1: it may load more rows than the provided LIMIT because it loads all values equal to the first cursor value + limit values greater.
-   *         This is needed to ensure that it does not accidentally skip duplicate values when the limit falls in the middle of some duplicated values.
-   * Note 2: it does not send keys that have already been sent before.
+   * Note 1: May load more rows than `limit` because it includes all rows equal to the
+   *         cursor value. This prevents skipping duplicates when limit falls mid-duplicates.
+   * Note 2: Skips keys that have already been sent to prevent duplicates.
    *
-   * @returns true if local data was found and sent, false if the local index was exhausted
+   * @returns true if local data was found, false if no more matching rows exist locally
    */
   requestLimitedSnapshot({
     orderBy,
@@ -635,12 +638,8 @@ export class CollectionSubscription
     this.loadedSubsets.push(loadOptions)
     this.trackLoadSubsetPromise(syncResult)
 
-    // Return whether local data was found and iteration completed normally.
-    // Return false if:
-    // - No local data was found (index exhausted)
-    // - Iteration limit was hit (abnormal exit)
-    // Either case signals that the caller should stop trying to load more.
-    // The async loadSubset may still return data later.
+    // Return true if we found and sent local data, false otherwise.
+    // The async loadSubset call may still fetch data from the backend.
     return changes.length > 0 && !hitIterationLimit
   }