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/store/runs.go

@@ -154,6 +154,45 @@ func (r *Runs) LatestForHost(ctx context.Context, hostID int64) (*model.Run, err
 	return &run, nil
 }
 
+// ListForHost returns the most recent `limit` runs for a host, newest
+// first. Caller uses this to drive the host-detail runs sidebar (last 20
+// by default, Phase 2). Zero/negative limit falls back to a safe cap so
+// a mistaken call can't scan the whole history into memory.
+func (r *Runs) ListForHost(ctx context.Context, hostID int64, limit int) ([]model.Run, error) {
+	if limit <= 0 {
+		limit = 20
+	}
+	rows, err := r.DB.QueryContext(ctx, `
+		SELECT id, host_id, state, COALESCE(result,''), COALESCE(failed_stage,''),
+		       COALESCE(next_boot_target,''), agent_token_hash, started_at,
+		       completed_at, COALESCE(report_path,''), COALESCE(hold_ip,''),
+		       COALESCE(override_flags_json,''), COALESCE(non_destructive,0)
+		FROM runs
+		WHERE host_id = ?
+		ORDER BY id DESC
+		LIMIT ?
+	`, hostID, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []model.Run
+	for rows.Next() {
+		var run model.Run
+		var completedAt sql.NullTime
+		if err := rows.Scan(&run.ID, &run.HostID, &run.State, &run.Result, &run.FailedStage,
+			&run.NextBootTarget, &run.AgentTokenHash, &run.StartedAt,
+			&completedAt, &run.ReportPath, &run.HoldIP, &run.OverrideFlagsJSON, &run.NonDestructive); err != nil {
+			return nil, err
+		}
+		if completedAt.Valid {
+			run.CompletedAt = &completedAt.Time
+		}
+		out = append(out, run)
+	}
+	return out, rows.Err()
+}
+
 // Active returns all runs in non-terminal states.
 func (r *Runs) Active(ctx context.Context) ([]model.Run, error) {
 	rows, err := r.DB.QueryContext(ctx, `