ui: GitHub-Actions-style detail page, sub-steps, mini-tile run-view

Reshapes the detail page into a run-view: hybrid horizontal pipeline
+ expanded active-step pane with sub-steps, a per-step log pane with
line-numbered permalinks and client-side search, and a runs-history
sidebar that navigates via ?run=N. Default step is server-picked
(running → failed → Reporting) so the operator lands on the thing
that's moving.

Adds a sub_steps table + SSE topic (substep-{run}-{stage}-{ordinal})
so per-disk and per-pass work (SMART, CPUStress CPU/RAM, Storage,
GPU) is visible in the UI instead of buried in stage summary JSON.
Agent emits sub-step reports from existing per-iteration loops.

Dashboard tiles become a mini run-view with a 9-dot step strip so
the operator reads run health across the whole grid at a glance.
Register page gets the same card shell + button styling.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

internal/httpserver/sse_e2e_test.go

@@ -143,3 +143,69 @@ func waitForSSEEvent(r *bufio.Reader, name string, timeout time.Duration) error
 type timeoutErr struct{}
 
 func (e *timeoutErr) Error() string { return "timeout waiting for sse event" }
+
+// TestSSE_SubStepEvent confirms PublishSubStepUpdate lands on the wire
+// with the exact "substep-{runID}-{stage}-{ordinal}" event name that
+// detail-page swap targets key on. Without this, the template renders
+// the right attribute but a middleware or renderer regression silently
+// drops the payload.
+func TestSSE_SubStepEvent(t *testing.T) {
+	conn, err := db.Open(filepath.Join(t.TempDir(), "vetting.db"))
+	if err != nil {
+		t.Fatalf("open db: %v", err)
+	}
+	t.Cleanup(func() { _ = conn.Close() })
+
+	hosts := &store.Hosts{DB: conn}
+	runs := &store.Runs{DB: conn}
+	stages := &store.Stages{DB: conn}
+	diffs := &store.SpecDiffs{DB: conn}
+	arts := &store.Artifacts{DB: conn}
+	hub := events.NewHub()
+	runner := &orchestrator.Runner{Runs: runs, Hosts: hosts, Stages: stages, EventHub: hub}
+	tiles := &api.TileEnricher{Runs: runs, Artifacts: arts, SpecDiffs: diffs}
+
+	orchestrator.SubStepRenderer = func(_ model.SubStep) string {
+		return `<div class="substep">row</div>`
+	}
+
+	ui := &api.UI{
+		Hosts: hosts, Runs: runs, Stages: stages, SpecDiffs: diffs, Artifacts: arts,
+		EventHub: hub, Runner: runner, Tiles: tiles,
+	}
+	agent := &api.Agent{
+		Hosts: hosts, Runs: runs, Stages: stages, Artifacts: arts,
+		SpecDiffs: diffs, Runner: runner, EventHub: hub,
+	}
+
+	router := NewRouter(Deps{UI: ui, Agent: agent})
+	srv := httptest.NewServer(router)
+	t.Cleanup(srv.Close)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+	defer cancel()
+	req, _ := http.NewRequestWithContext(ctx, http.MethodGet, srv.URL+"/events", nil)
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		t.Fatalf("GET /events: %v", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	reader := bufio.NewReader(resp.Body)
+	if err := waitForSSEEvent(reader, "hello", 1*time.Second); err != nil {
+		t.Fatalf("hello preamble: %v", err)
+	}
+	time.Sleep(50 * time.Millisecond)
+
+	runner.PublishSubStepUpdate(context.Background(), model.SubStep{
+		RunID:     42,
+		StageName: "CPUStress",
+		Ordinal:   1,
+		Name:      "Memory pass",
+		State:     model.StagePassed,
+	})
+
+	if err := waitForSSEEvent(reader, "substep-42-CPUStress-1", 2*time.Second); err != nil {
+		t.Fatalf("substep event: %v", err)
+	}
+}