fix(env): check vpx shim in vp env doctor (#876)

## Summary

- `vp env setup` creates shims for `["node", "npm", "npx", "vpx"]`
- `vp env doctor` only checked `["node", "npm", "npx"]`, missing `vpx`
- A broken or missing `vpx` shim was invisible to the doctor

Fixes #880

One-line change in `crates/vite_global_cli/src/commands/env/doctor.rs`.

## Context

`setup.rs:24` defines:
```rust
const SHIM_TOOLS: &[&str] = &["node", "npm", "npx", "vpx"];
```

But `doctor.rs:25` had:
```rust
const SHIM_TOOLS: &[&str] = &["node", "npm", "npx"];
```

This also means the PATH section's tool-resolution check (line 373)
skipped `vpx`.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: MK (fengmk2) <fengmk2@gmail.com>

Author: 3 people

crates/vite_global_cli/src/commands/env/doctor.rs

@@ -22,7 +22,7 @@ const KNOWN_VERSION_MANAGERS: &[(&str, &str)] = &[
 ];
 
 /// Tools that should have shims
-const SHIM_TOOLS: &[&str] = &["node", "npm", "npx"];
+const SHIM_TOOLS: &[&str] = &["node", "npm", "npx", "vpx"];
 
 /// Column width for left-side keys in aligned output
 const KEY_WIDTH: usize = 18;