fix: fire setDirty when pager fetch pipeline drains (closes #298)

When a static camera is combined with on-demand rendering, the
onDirty chain breaks during paged LOD loading because chunk fetches
complete asynchronously — outside any render frame — and nothing
signals the renderer that new data is ready to process.

Fix: call setDirty() at two points in SplatPager:
- when fetchers drains to 0 (all in-flight downloads finished)
- when processFetched() fully empties the fetched queue

The consumeLodTreeUpdates path is intentionally unchanged; SparkRenderer
already calls setDirty() there via the existing lodDirty flow.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: onderilkesever

dist/spark.cjs.js

@@ -84,6 +84,7 @@ export interface SplatPagerOptions {
      * @default 3
      */
     numFetchers?: number;
+    onDirty?: () => void;
 }
 export declare class SplatPager {
     renderer: THREE.WebGLRenderer;
@@ -96,6 +97,7 @@ export declare class SplatPager {
     autoDrive: boolean;
     numFetchers: number;
     fetchPause: number;
+    onDirty?: () => void;
     splatsChunkToPage: Map<PagedSplats, ({
         page: number;
         lru: number;

dist/spark.cjs.js.map

@@ -1233,6 +1233,7 @@ export class SparkRenderer extends THREE.Mesh {
           extSplats: this.pagedExtSplats,
           maxSplats: this.maxPagedSplats,
           numFetchers: this.numLodFetchers,
+          onDirty: () => this.setDirty(),
         });
 
         const { lodId } = (await worker.call("newLodTree", {

dist/spark.module.js

@@ -462,6 +462,7 @@ export interface SplatPagerOptions {
    * @default 3
    */
   numFetchers?: number;
+  onDirty?: () => void;
 }
 
 export class SplatPager {
@@ -478,6 +479,7 @@ export class SplatPager {
   autoDrive: boolean;
   numFetchers: number;
   fetchPause = 0;
+  onDirty?: () => void;
 
   splatsChunkToPage: Map<
     PagedSplats,
@@ -573,6 +575,7 @@ export class SplatPager {
 
     this.autoDrive = options.autoDrive ?? true;
     this.numFetchers = options.numFetchers ?? 3;
+    this.onDirty = options.onDirty;
 
     this.splatsChunkToPage = new Map();
     this.pageToSplatsChunk = new Array(this.maxPages);
@@ -1277,6 +1280,7 @@ export class SplatPager {
             this.fetchers = this.fetchers.filter(
               ({ splats: s, chunk: c }) => splats !== s || chunk !== c,
             );
+            if (this.fetchers.length === 0) this.onDirty?.();
             this.processFetched();
           });
         // Add self to active fetchers list
@@ -1336,11 +1340,14 @@ export class SplatPager {
 
   private processFetched() {
     const now = performance.now();
+    let processed = false;
     while (true) {
       const fetched = this.fetched.shift();
       if (!fetched) {
+        if (processed) this.onDirty?.();
         break;
       }
+      processed = true;
       const { splats, chunk, data } = fetched;
 
       let page = this.allocatePage();