chore(global_cli): clarify --help for vp env default/pin/use/exec (#1664)

## Summary

Closes #949.

Adds `Examples:` blocks (via clap `after_help`) to the four `vp env`
subcommands flagged in the issue, so the intended invocation modes are
visible directly from `--help`:

- `vp env default` — show vs. set (with/without `<version>`)
- `vp env pin` — show / pin / range / `--unpin`
- `vp env use` — default / override `<version>` / `--unset`
- `vp env exec` — explicit `--node <version>` vs. shim mode

Also tightens per-argument doc comments ("If not provided" → "If
omitted", missing period).

No behavior changes. The clap auto-generated `Usage:` line is unchanged.

The `command-env-use` snap was regenerated to capture the new `--help`
output.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-authored-by: MK <fengmk2@gmail.com>

Author: 3 people

crates/vite_global_cli/src/cli.rs

@@ -298,9 +298,13 @@ pub enum EnvSubcommands {
     Print,
 
     /// Set or show the global default Node.js version
+    #[command(after_long_help = "\
+Examples:
+  vp env default          # Show the current default
+  vp env default lts      # Set the default")]
     Default {
-        /// Version to set as default (e.g., "20.18.0", "lts", "latest")
-        /// If not provided, shows the current default
+        /// Version to set as default (e.g., "20.18.0", "lts", "latest").
+        /// If omitted, prints the current default.
         version: Option<String>,
     },
 
@@ -330,9 +334,14 @@ pub enum EnvSubcommands {
     },
 
     /// Pin a Node.js version in the current directory (creates .node-version)
+    #[command(after_long_help = "\
+Examples:
+  vp env pin lts                  # Pin to latest LTS
+  vp env pin --unpin              # Remove .node-version
+  vp env pin \"^20.0.0\" --force    # Overwrite existing pin")]
     Pin {
-        /// Version to pin (e.g., "20.18.0", "lts", "latest", "^20.0.0")
-        /// If not provided, shows the current pinned version
+        /// Version to pin (e.g., "20.18.0", "lts", "latest", "^20.0.0").
+        /// If omitted, prints the currently pinned version.
         version: Option<String>,
 
         /// Remove the .node-version file from current directory
@@ -383,11 +392,17 @@ pub enum EnvSubcommands {
     },
 
     /// Execute a command with a specific Node.js version
-    #[command(visible_alias = "run")]
+    #[command(
+        visible_alias = "run",
+        after_long_help = "\
+Examples:
+  vp env exec --node lts npm install  # Pin version for this invocation
+  vp env exec node -v                 # Shim mode: version auto-resolved"
+    )]
     Exec {
-        /// Node.js version to use (e.g., "20.18.0", "lts", "^20.0.0")
-        /// If not provided and command is node/npm/npx or a global package binary,
-        /// version is resolved automatically (same as shim behavior)
+        /// Node.js version to use (e.g., "20.18.0", "lts", "^20.0.0").
+        /// If omitted and command is node/npm/npx or a global package binary,
+        /// version is resolved automatically (same as shim behavior).
         #[arg(long)]
         node: Option<String>,
 
@@ -417,9 +432,13 @@ pub enum EnvSubcommands {
     },
 
     /// Use a specific Node.js version for this shell session
+    #[command(after_long_help = "\
+Examples:
+  vp env use lts        # Override session with latest LTS
+  vp env use --unset    # Clear the session override")]
     Use {
-        /// Version to use (e.g., "20", "20.18.0", "lts", "latest")
-        /// If not provided, reads from .node-version or package.json
+        /// Version to use (e.g., "20", "20.18.0", "lts", "latest").
+        /// If omitted, reads from .node-version or package.json.
         version: Option<String>,
 
         /// Remove session override (revert to file-based resolution)

packages/cli/snap-tests-global/command-env-use/snap.txt

@@ -4,13 +4,17 @@ Usage: vp env use [OPTIONS] [VERSION]
 Use a specific Node.js version for this shell session
 
 Arguments:
-  [VERSION]  Version to use (e.g., "20", "20.18.0", "lts", "latest") If not provided, reads from .node-version or package.json
+  [VERSION]  Version to use (e.g., "20", "20.18.0", "lts", "latest"). If omitted, reads from .node-version or package.json
 
 Options:
   --unset                Remove session override (revert to file-based resolution)
   --no-install           Skip auto-installation if version not present
   --silent-if-unchanged  Suppress output if version is already active
-  -h, --help             Print help
+  -h, --help             Print help (see a summary with '-h')
+
+Examples:
+  vp env use lts        # Override session with latest LTS
+  vp env use --unset    # Clear the session override
 
 Documentation: https://viteplus.dev/guide/env