fix(rust): handle rustup check exit code 100 as non-error (#8832)

## Summary

Fixes the issue where `mise outdated` fails when rust toolchain updates
are
  available.

  ## Problem

`rustup check` returns exit code 100 when toolchain updates are
available, which
is normal behavior and not an error. Previously, mise treated this as a
failure,
  causing `mise outdated` to report:

Error getting outdated info for core:rust@stable: command ["rustup",
"check"]
  exited with code 100

  ## Solution

Changed the `outdated_info` method in `src/plugins/core/rust.rs` to use
`.unchecked().run()` instead of `.read()`, allowing mise to manually
handle the
  exit code and parse the output correctly even when rustup returns 100.

  ## Testing

  - Built successfully with `cargo build --release`
  - Verified with `cargo check`
  EOF

---------

Co-authored-by: greptile-apps[bot] <165735046+greptile-apps[bot]@users.noreply.github.com>

Author: shalk

src/plugins/core/rust.rs

@@ -222,7 +222,19 @@ impl Backend for RustPlugin {
             for (k, v) in self.exec_env(config, ts, tv).await? {
                 cmd = cmd.env(k, v);
             }
-            let out = cmd.read()?;
+            // rustup check returns exit code 100 when updates are available
+            // This is not an error, so we use unchecked() and check status manually
+            let result = cmd.stdout_capture().stderr_capture().unchecked().run()?;
+            let exit_code = result.status.code().unwrap_or(-1);
+            if exit_code != 0 && exit_code != 100 {
+                let stderr = String::from_utf8_lossy(&result.stderr);
+                eyre::bail!(
+                    "command [\"rustup\", \"check\"] exited with code {}. stderr: {}",
+                    exit_code,
+                    stderr.trim()
+                );
+            }
+            let out = String::from_utf8_lossy(&result.stdout);
             for line in out.lines() {
                 if line.starts_with(&self.target_triple(tv))
                     && let Some(_cap) = v_re.captures(line)