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>

agent/runner.go

@@ -276,6 +276,25 @@ func postResult(ctx context.Context, c *Client, stage string, s stageOutcome) (*
 	if s.Inventory != nil {
 		body["inventory"] = s.Inventory
 	}
+	if len(s.Outcome.SubSteps) > 0 {
+		wire := make([]SubStepReport, 0, len(s.Outcome.SubSteps))
+		for _, ss := range s.Outcome.SubSteps {
+			w := SubStepReport{
+				Name:    ss.Name,
+				Passed:  ss.Passed,
+				Skipped: ss.Skipped,
+				Summary: ss.SummaryJSON,
+			}
+			if !ss.StartedAt.IsZero() {
+				w.StartedAt = ss.StartedAt.UTC().Format(time.RFC3339Nano)
+			}
+			if !ss.CompletedAt.IsZero() {
+				w.CompletedAt = ss.CompletedAt.UTC().Format(time.RFC3339Nano)
+			}
+			wire = append(wire, w)
+		}
+		body["sub_steps"] = wire
+	}
 	return c.Result(ctx, body)
 }