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/api/tile.go

@@ -19,6 +19,7 @@ import (
 // place that renders a tile shows the same data.
 type TileEnricher struct {
 	Runs      *store.Runs
+	Stages    *store.Stages
 	Artifacts *store.Artifacts
 	SpecDiffs *store.SpecDiffs
 }
@@ -53,6 +54,16 @@ func (e *TileEnricher) Build(ctx context.Context, host model.Host, latest *model
 			log.Printf("tile: list artifacts run %d: %v", latest.ID, err)
 		}
 	}
+	// Stage row per canonical stage drives the dashboard tile's mini
+	// run-view strip. Fail-soft: a DB hiccup renders the tile without
+	// dots rather than breaking the whole dashboard.
+	if e.Stages != nil {
+		if stages, err := e.Stages.ListForRun(ctx, latest.ID); err == nil {
+			t.Stages = stages
+		} else {
+			log.Printf("tile: list stages run %d: %v", latest.ID, err)
+		}
+	}
 	return t
 }