test(plan): update windows-only task_graph snapshot to commands array

The `windows_cmd_shim_rewrite` fixture was missed when ResolvedTaskConfig
switched from `command: Str` to `commands: Arc<[Str]>`. The fixture is
gated to `cfg(windows)` so non-Windows local runs skip it, but CI on
Windows fails. Updates the singular `"command"` field to the new array
form.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: wan9chi

crates/vite_task_plan/tests/plan_snapshots/fixtures/windows_cmd_shim_rewrite/snapshots/task_graph.jsonc

@@ -12,7 +12,9 @@
         "package_path": "<workspace>/packages/foo"
       },
       "resolved_config": {
-        "command": "vite --port 3000",
+        "commands": [
+          "vite --port 3000"
+        ],
         "resolved_options": {
           "cwd": "<workspace>/packages/foo",
           "cache_config": {