feat(skills): add optional shell command runner

src/cli/skills.test.ts

@@ -23,6 +23,7 @@ import {
   mergeInstallerExecutionResults,
   runInstallerCommandsWithPolicy,
   noOpSkillInstallerCommandRunner,
+  createShellSkillInstallerCommandRunner,
   runSkillInstallAction,
 } from './skills.js';
 import type { Skill } from '../skills/index.js';
@@ -376,6 +377,33 @@ describe('skills CLI helpers', () => {
     expect(runner.run).toHaveBeenCalledWith(['brew install jq']);
   });
 
+  it('shell command runner reports succeeded command status', () => {
+    const runner = createShellSkillInstallerCommandRunner();
+
+    const results = runner.run(['node -e "process.exit(0)"']);
+
+    expect(results).toEqual([
+      {
+        command: 'node -e "process.exit(0)"',
+        status: 'succeeded',
+      },
+    ]);
+  });
+
+  it('shell command runner reports failed command with exit code reason', () => {
+    const runner = createShellSkillInstallerCommandRunner();
+
+    const results = runner.run(['node -e "process.exit(7)"']);
+
+    expect(results).toEqual([
+      {
+        command: 'node -e "process.exit(7)"',
+        status: 'failed',
+        reason: 'exit_code_7',
+      },
+    ]);
+  });
+
   it('maps runner command results into structured per-step statuses', () => {
     const attempted = [
       { installer_type: 'brew', command: 'brew install jq' },