test(snapshots): keep first-start setup off the npm registry

crates/vp_cli_snapshots/tests/cli_snapshots/README.md

@@ -243,7 +243,10 @@ preference inference or an empty installation must create a separate home, as th
 `shim_package_manager_setup` fixture does.
 The preparation command sets `VP_SELF_SETUP_NO_MODIFY_PATH=1` so Windows
 self-setup does not add temporary case homes to the user's persistent `PATH`.
-This override applies only to runner preparation, not to fixture commands.
+It also sets `VP_SKIP_DEPS_INSTALL=1`: the case home already has the checkout
+package, and setup would otherwise look up the build's version on npm, which
+is unpublished on a release branch.
+These overrides apply only to runner preparation, not to fixture commands.
 
 A step is a bare argv array or a table:
 

crates/vp_cli_snapshots/tests/cli_snapshots/fixtures/snapshot_setup/verify.mjs

@@ -9,6 +9,7 @@ const referenceHome = path.resolve('reference-home');
 const reference = path.join(referenceHome, '.vite-plus');
 const windows = process.platform === 'win32';
 assert.equal(process.env.VP_SELF_SETUP_NO_MODIFY_PATH, undefined);
+assert.equal(process.env.VP_SKIP_DEPS_INSTALL, undefined);
 if (windows) {
   const result = spawnSync(
     'powershell.exe',
@@ -46,10 +47,14 @@ for (const name of Object.keys(env)) {
     delete env[name];
   }
 }
+// Match the runner's preparation overrides. Without VP_SKIP_DEPS_INSTALL,
+// setup looks up the platform package for the binary version on npm, which
+// does not exist until that version is released.
 Object.assign(env, {
   VP_HOME: reference,
   VP_CLI_TEST: '1',
   VP_SELF_SETUP_NO_MODIFY_PATH: '1',
+  VP_SKIP_DEPS_INSTALL: '1',
   HOME: referenceHome,
   USERPROFILE: referenceHome,
   PATH: windows

crates/vp_cli_snapshots/tests/cli_snapshots/main.rs

@@ -746,6 +746,12 @@ impl CaseHome {
             // to the real user's persistent PATH. Case commands do not
             // inherit this override, so self-setup fixtures retain coverage.
             .env("VP_SELF_SETUP_NO_MODIFY_PATH", "1")
+            // The checkout package is already installed in this home. Without
+            // this, a build with no `vp-install-lock.yaml` beside it looks up
+            // its own version's platform package on npm, which does not exist
+            // on a release branch before publishing. Case commands do not
+            // inherit this override either.
+            .env("VP_SKIP_DEPS_INSTALL", "1")
             .output()
             .map_err(|e| format!("failed to run first-start setup: {e}"))?;
         if output.status.success() {