fix(skills): generate executable download install plans

src/skills/planner.test.ts

@@ -55,8 +55,20 @@ describe('buildInstallerPlan', () => {
     expect(plan.steps).toEqual([
       { installerType: 'go', command: 'go install example.com/tool/a@latest' },
       { installerType: 'go', command: 'go install example.com/tool/b@latest' },
-      { installerType: 'download', command: 'download https://example.com/tool.tgz -> /tmp/tool.tgz' },
+      { installerType: 'download', command: 'curl -fsSL -o /tmp/tool.tgz https://example.com/tool.tgz' },
     ]);
     expect(plan.skipped).toEqual([]);
   });
+
+  it('skips download installer when destination is missing', () => {
+    const plan = buildInstallerPlan(
+      [{ type: 'download', url: 'https://example.com/tool.tgz' }],
+      { hasBinary: () => true },
+    );
+
+    expect(plan.steps).toEqual([]);
+    expect(plan.skipped).toEqual([
+      { installerType: 'download', reason: 'download destination is required for executable install plans' },
+    ]);
+  });
 });

src/skills/planner.ts

@@ -73,10 +73,13 @@ export function buildInstallerPlan(
       continue;
     }
 
-    const destination = installer.destination ?? '<default destination>';
+    if (!installer.destination) {
+      skipped.push({ installerType: 'download', reason: 'download destination is required for executable install plans' });
+      continue;
+    }
     steps.push({
       installerType: 'download',
-      command: `download ${installer.url} -> ${destination}`,
+      command: `curl -fsSL -o ${installer.destination} ${installer.url}`,
     });
   }