fix: don't override loadGraphData viewport on cache miss (#10810)

## Summary

Fix regression from #10247 where template workflows (e.g. LTX2.3) loaded
with a broken viewport.

## Problem

`restoreViewport()` called `fitView()` on every cache miss via rAF. This
raced with `loadGraphData`'s own viewport restore (`extra.ds` for saved
workflows, or its own `fitView()` for templates at line 1266 of app.ts).
The second `fitView()` overwrote the correct viewport, causing templates
with subgraphs to display incorrectly.

## Fix

On cache miss, check if any nodes are already visible in the current
viewport before calling `fitView()`. If `loadGraphData` already
positioned things correctly, we don't override it. Only intervene when
the viewport is genuinely empty (first visit to a subgraph with no prior
cached state AND no loadGraphData restore).

## Review Focus

Single-file change in `subgraphNavigationStore.ts`. The visibility check
mirrors the same pattern used in `app.ts:1272-1281` where loadGraphData
itself checks for visible nodes.

## E2E Regression Test

The existing Playwright tests in
`browser_tests/tests/subgraphViewport.spec.ts` (added in #10247) already
cover viewport restoration after subgraph navigation. The specific
regression (template load viewport race) is not practically testable in
E2E because:
1. Template loading requires the backend's template API which returns
different templates per environment
2. The race condition depends on exact timing between `loadGraphData`'s
viewport restore and the rAF-deferred `restoreViewport` — Playwright
cannot reliably reproduce frame-level timing races
3. The fix is a guard condition (skip fitView if nodes visible) that
makes the behavior idempotent regardless of timing

## Alternative to #10790

This can replace the full revert in #10790 — it preserves the viewport
persistence feature while fixing the template regression.

Fixes regression from #10247

src/stores/subgraphNavigationStore.ts

@@ -12,6 +12,7 @@ import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
 import { useLitegraphService } from '@/services/litegraphService'
 import { app } from '@/scripts/app'
 import { findSubgraphPathById } from '@/utils/graphTraversalUtil'
+import { anyItemOverlapsRect } from '@/utils/mathUtil'
 import { isNonNullish, isSubgraph } from '@/utils/typeGuardUtil'
 
 export const VIEWPORT_CACHE_MAX_SIZE = 32
@@ -138,11 +139,19 @@ export const useSubgraphNavigationStore = defineStore(
         return
       }
 
-      // Cache miss — fit to content after the canvas has the new graph.
-      // rAF fires after layout + paint, when nodes are positioned.
-      const expectedGraphId = graphId
+      // Cache miss — fit to content only if no nodes are currently visible.
+      // loadGraphData may have already restored extra.ds or called fitView
+      // for templates, so only intervene when the viewport is truly empty.
       requestAnimationFrame(() => {
-        if (getActiveGraphId() !== expectedGraphId) return
+        if (getActiveGraphId() !== graphId) return
+        if (!canvas.graph) return
+
+        const nodes = canvas.graph.nodes
+        if (!nodes?.length) return
+
+        canvas.ds.computeVisibleArea(canvas.viewport)
+        if (anyItemOverlapsRect(nodes, canvas.ds.visible_area)) return
+
         useLitegraphService().fitView()
       })
     }

src/stores/subgraphNavigationStore.viewport.test.ts

@@ -24,8 +24,11 @@ vi.mock('@/scripts/app', () => {
       scale: 1,
       offset: [0, 0],
       state: { scale: 1, offset: [0, 0] },
-      fitToBounds: vi.fn()
+      fitToBounds: vi.fn(),
+      visible_area: [0, 0, 1000, 1000],
+      computeVisibleArea: vi.fn()
     },
+    viewport: [0, 0, 1000, 1000],
     setDirty: mockSetDirty,
     get empty() {
       return true
@@ -184,6 +187,11 @@ describe('useSubgraphNavigationStore - Viewport Persistence', () => {
       // Ensure no cached entry
       store.viewportCache.delete(':root')
 
+      // Add a node outside the visible area so anyItemOverlapsRect returns false
+      const mockGraph = app.graph as { nodes: unknown[]; _nodes: unknown[] }
+      mockGraph.nodes = [{ pos: [9999, 9999], size: [100, 100] }]
+      mockGraph._nodes = mockGraph.nodes
+
       // Use the root graph ID so the stale-guard passes
       store.restoreViewport('root')
 
@@ -194,6 +202,10 @@ describe('useSubgraphNavigationStore - Viewport Persistence', () => {
       rafCallbacks[0](performance.now())
 
       expect(mockFitView).toHaveBeenCalledOnce()
+
+      // Cleanup
+      mockGraph.nodes = []
+      mockGraph._nodes = []
     })
 
     it('skips fitView if active graph changed before rAF fires', () => {