fix: clear modelWarming notice when job completes via SSE done event

Previously, if a job completed while the model-warming notice was shown
(e.g. model loaded mid-job), the 'Warming up model' banner persisted on
the Done screen because the SSE 'done' handler didn't clear modelWarming.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/routes/jobs/[id]/+page.svelte

@@ -92,6 +92,7 @@
 				} else if (data.type === 'status') {
 					if (job) job = { ...job, status: data.status, progress: data.progress ?? job.progress };
 				} else if (data.type === 'done') {
+					modelWarming = null;
 					eventSource?.close();
 					loadJob();
 				} else if (data.type === 'error') {