fix: remove redundant skill copy from sync-ecc-to-codex.sh

Codex CLI reads skills natively from ~/.agents/skills/ (installed by
ECC installer / npx skills). The sync script was redundantly copying
the same skills from .agents/skills/ to ~/.codex/skills/.

Changes:
- Remove skill copy loop, variables, and path validation from sync script
- Update sanity checker to validate ~/.agents/skills/ instead of
  ~/.codex/skills/, downgrade missing skills from FAIL to WARN
- Update test assertions to verify skill sync removal

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

tests/scripts/sync-ecc-to-codex.test.js

@@ -69,8 +69,9 @@ function runTests() {
 
   if (test('filesystem-changing calls use argv-form run_or_echo invocations', () => {
     assert.ok(source.includes('run_or_echo mkdir -p "$BACKUP_DIR"'), 'mkdir should use argv form');
-    assert.ok(source.includes('run_or_echo rm -rf "$dest"'), 'rm should use argv form');
-    assert.ok(source.includes('run_or_echo cp -R "$skill_dir" "$dest"'), 'recursive copy should use argv form');
+    // Skills sync rm/cp calls were removed — Codex reads from ~/.agents/skills/ natively
+    assert.ok(!source.includes('run_or_echo rm -rf "$dest"'), 'skill sync rm should be removed');
+    assert.ok(!source.includes('run_or_echo cp -R "$skill_dir" "$dest"'), 'skill sync cp should be removed');
   })) passed++; else failed++;
 
   console.log(`\nResults: Passed: ${passed}, Failed: ${failed}`);