fix: restore process.env spread in skill check execa call

Without spreading process.env, execa replaces the entire environment
when env is passed, so npx has no PATH and fails silently. Also
reports skill check errors to PostHog via errorReporter.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Paveltarno

packages/cli/src/cli/utils/skill-version-check.ts

@@ -37,7 +37,7 @@ async function listInstalledSkills(
   const { stdout } = await execa("npx", ["-y", "skills", "list", "--json"], {
     cwd,
     timeout: 3000,
-    env: { CI: "1" },
+    env: { ...process.env, CI: "1" },
   });
 
   // npx may emit non-JSON preamble (download progress, warnings) before the array