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/web/templates/dashboard.templ

@@ -9,10 +9,14 @@ import (
 // TileData pairs a host with its latest run and the derived fields the
 // tile needs to render: spec-diff count (server-side diff result) and
 // the on-disk path to the hold-key artifact when the run is holding.
-// LastSeenAt is the host-mode agent's most recent heartbeat.
+// LastSeenAt is the host-mode agent's most recent heartbeat. Stages is
+// the list of canonical-order stage rows for Latest, used by HostTile
+// to render the mini run-view; nil/empty for never-run hosts (a ghost
+// dot strip is rendered from DefaultStageOrder).
 type TileData struct {
 	Host             model.Host
 	Latest           *model.Run
+	Stages           []model.Stage
 	SpecDiffCritical int
 	HoldKeyPath      string
 	LastSeenAt       *time.Time