fix: prevent race condition when navigation changes during head() re-execution

Addresses two scenarios:
1. New navigation starts BEFORE scheduled head() executes
2. New navigation starts WHILE head() is executing

Solution:
- Capture this navigation's location (thisNavigationLocation)
- Before executing head(), check if router's current location matches
- If location changed (new navigation), skip stale head() execution
- Location objects are always unique (parseLocation creates new objects)

Both concerns are resolved:
- Scenario 1: Location check prevents stale head() from executing
- Scenario 2: Stale head() may complete but fresh navigation
  overwrites with correct data immediately after

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: yanghuidong

packages/router-core/src/load-matches.ts

@@ -959,7 +959,14 @@ export async function loadMatches(arg: {
     if (asyncLoaderPromises.length > 0) {
       // Schedule re-execution after all async loaders complete (non-blocking)
       // Use allSettled to handle both successful and failed loaders
-      Promise.allSettled(asyncLoaderPromises).then(() => executeAllHeadFns(inner))
+      const thisNavigationLocation = inner.location
+      Promise.allSettled(asyncLoaderPromises).then(() => {
+        // Only execute if this navigation is still current (not superseded by new navigation)
+        const latestLocation = inner.router.state.location
+        if (latestLocation === thisNavigationLocation) {
+          executeAllHeadFns(inner)
+        }
+      })
     }
 
     // Throw notFound after head execution