Pane state: clear network host on leaving the network volume

`currentNetworkHost` in FilePane was only reset when the user clicked Back inside ShareBrowser. Volume-switches via the picker / breadcrumb / history nav / MCP left the host pinned: re-entering Network re-mounted NetworkMountView with the stale `initialNetworkHost`, which renders ShareBrowser for that host instead of the host list.

In the SMB E2E suite this manifested as a chain: test #4 (`mounting guest share`) opens guest, the next test's beforeEach switches the pane to local, then the test re-selects Network — and lands on ShareBrowser for guest instead of NetworkBrowser. `cmdr://state` then contains the share list of guest's public share, not the 14-host roster, so `state.includes('SMB Test (Guest)') && state.includes('shares=1')` is never true and the spec hits its 30s pollUntil deadline.

Fix: a `$effect` in FilePane clears `currentNetworkHost` whenever `isNetworkView` becomes false. Re-entry now always lands on the host list. This matches the gotcha already documented in `file-explorer/network/CLAUDE.md` ('previous test that mounted a guest share left FilePane stuck on guest').

Author: vdavid

apps/desktop/src/lib/file-explorer/pane/FilePane.svelte

@@ -423,6 +423,24 @@
     // Network browsing state - tracked here for history navigation integration
     let currentNetworkHost = $state<NetworkHost | null>(null)
 
+    // Clear the selected network host whenever the pane leaves the network
+    // volume so that re-entering Network always lands on the host list, not on
+    // a stale ShareBrowser for whichever host was open last. Without this,
+    // `NetworkMountView` re-mounts with the old `initialNetworkHost` and the
+    // user sees the previous share list when they expected the host list.
+    //
+    // Previously this only got cleared by an explicit "Back" click inside
+    // `ShareBrowser` (which calls `onNetworkHostChange(null)`). Volume-switches
+    // via the picker, the breadcrumb, history navigation, or MCP didn't trip
+    // that path, so the host stayed pinned. The matching gotcha in
+    // `file-explorer/network/CLAUDE.md` documented this as the cause of E2E
+    // test 436 ("unicode shares render") and several SMB share-count tests.
+    $effect(() => {
+        if (!isNetworkView && currentNetworkHost !== null) {
+            currentNetworkHost = null
+        }
+    })
+
     // noinspection JSUnusedGlobalSymbols -- Used dynamically
     export function toggleVolumeChooser() {
         volumeBreadcrumbRef?.toggle()