fix(local-model): a switch or a new model from a stopped model undoes the Stop

A job started from a model the person had stopped runs the runtime, and
the model it ends on is in use and running. The stored "stopped" flag
stayed set, so that model would not have started with the server again.
Both verbs now set it back once their job started, the way Start does.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

test/local-model-install-service.test.ts

@@ -3046,6 +3046,31 @@ describe('use: the switch to a checked model', () => {
     expect(h.store.get().state).toBe('installed');
   });
 
+  it('a switch or a new model from a stopped model starts the runtime and undoes the Stop', async () => {
+    const stopped: LocalModelStateFile = { ...TWO_MODELS, runtime: { ...INSTALLED.runtime!, enabled: false } };
+    const switched = setup({ state: stopped, runtimeOnDisk: true, agentInstalled: true });
+    await switched.service.boot();
+    expect(switched.supervisor.start).not.toHaveBeenCalled();
+    await switched.service.use({ modelId: GPT.id }, ADMIN);
+    await switched.service.idle();
+    // The model is in use and running now, so it starts with the server again, like after Start.
+    expect(switched.store.get()).toMatchObject({ state: 'installed', runtime: { enabled: true } });
+    expect((await switched.service.view()).running).toBe(true);
+
+    const added = setup({ state: { ...INSTALLED, runtime: { ...INSTALLED.runtime!, enabled: false } } });
+    added.world.runtimeOnDisk = true;
+    added.world.agentInstalled = true;
+    await added.service.boot();
+    await added.service.install(ADD_GPT, ADMIN);
+    await added.service.idle();
+    expect(added.store.get()).toMatchObject({ state: 'installed', model: { id: GPT.id }, runtime: { enabled: true } });
+
+    // A switch that was refused changed nothing: the model stays stopped.
+    const refused = setup({ state: stopped, runtimeOnDisk: true, agentInstalled: true });
+    await refused.service.use({ modelId: 'someone-else:7b' }, ADMIN);
+    expect(refused.store.get().runtime?.enabled).toBe(false);
+  });
+
   it('Cancel pauses a switch like any job, and Resume goes on with it', async () => {
     const h = setup({
       state: TWO_MODELS,