test(check): verify real lint errors are not swallowed by suppress_unmatched

Add snap test that runs `vp check --fix` with paths (activating
suppress_unmatched) on a file with a real lint error, confirming the
error is still surfaced and the command exits non-zero.

Author: fengmk2

packages/cli/snap-tests/check-fix-lint-error-not-swallowed/.oxlintrc.json

@@ -0,0 +1,5 @@
+{
+  "rules": {
+    "no-eval": "error"
+  }
+}

packages/cli/snap-tests/check-fix-lint-error-not-swallowed/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "check-fix-lint-error-not-swallowed",
+  "version": "0.0.0",
+  "private": true
+}

packages/cli/snap-tests/check-fix-lint-error-not-swallowed/snap.txt

@@ -0,0 +1,12 @@
+[1]> vp check --fix src/index.js # real lint error with --fix and paths (suppress_unmatched active), error must not be swallowed
+error: Lint issues found
+× eslint(no-eval): eval can be harmful.
+   ╭─[src/index.js:2:3]
+ 1 │ function hello() {
+ 2 │   eval("code");
+   ·   ────
+ 3 │   return "hello";
+   ╰────
+  help: Avoid eval(). For JSON parsing use JSON.parse(); for dynamic property access use bracket notation (obj[key]); for other cases refactor to avoid evaluating strings as code.
+
+Found 1 error and 0 warnings in 1 file (<variable>ms, <variable> threads)

packages/cli/snap-tests/check-fix-lint-error-not-swallowed/src/index.js

@@ -0,0 +1,6 @@
+function hello() {
+  eval("code");
+  return "hello";
+}
+
+export { hello };

packages/cli/snap-tests/check-fix-lint-error-not-swallowed/steps.json

@@ -0,0 +1,5 @@
+{
+  "commands": [
+    "vp check --fix src/index.js # real lint error with --fix and paths (suppress_unmatched active), error must not be swallowed"
+  ]
+}