docs(test): add just snapshot-test-global for checkouts without a JS build

Round-8 review follow-up: absent dist stays a deliberate fail-fast with
remedies in the message (auto-building would drag the rolldown chain into
the recipe; auto-skipping would hide coverage), and toolchain-only
contributors get a first-class entry point instead.

Claude-Session: https://claude.ai/code/session_01NRgjMi2Vus3iJctudGEWPT

Author: fengmk2

crates/vite_cli_snapshots/tests/cli_snapshots/README.md

@@ -44,6 +44,7 @@ the stored snapshot. Never hand-edit `.md` snapshots; re-record instead.
 ```bash
 just snapshot-test                    # build vp, run everything
 just snapshot-test <substring>        # filter by trial name
+just snapshot-test-global             # no JS build needed (skips local flavor)
 UPDATE_SNAPSHOTS=1 just snapshot-test # accept snapshot changes
 pnpm snapshot-test                    # same, via pnpm
 cargo test -p vite_cli_snapshots -- <filter>      # if vp is already built

justfile

@@ -83,11 +83,23 @@ test:
 # PTY-based CLI snapshot tests (crates/vite_cli_snapshots). Builds the global
 # binary first so the harness never tests a stale build. Filter by trial name
 # substring: `just snapshot-test create`. Accept snapshot changes with
-# `UPDATE_SNAPSHOTS=1 just snapshot-test`.
+# `UPDATE_SNAPSHOTS=1 just snapshot-test`. Local-flavor cases additionally
+# need a built packages/cli (`pnpm build`); the harness fails fast when dist
+# is missing or stale. Use snapshot-test-global on checkouts without one.
 snapshot-test *args='':
   cargo build -p vite_global_cli
   cargo test -p vite_cli_snapshots -- {{args}}
 
+# Global flavor + vpt cases only: needs no JS build, for Rust-side work on
+# a checkout that never ran `pnpm build`.
+[unix]
+snapshot-test-global *args='':
+  VP_SNAP_SKIP_FLAVORS=local just snapshot-test {{args}}
+
+[windows]
+snapshot-test-global *args='':
+  $Env:VP_SNAP_SKIP_FLAVORS='local'; just snapshot-test {{args}}
+
 # Single source of truth for clippy, used by CI too. The `-A` flags allow
 # new toolchain lints that fire in upstream rolldown crates without a `[lints]` table.
 lint: