ui: split /hosts/{id} into host page + /runs/{runID} run page

Host page owns host metadata, full runs table with per-row stage strip,
in-flight banner, and empty-state CTA. Run page owns pipeline, active
step, logs, sub-steps, spec diffs, and hold banner with a breadcrumb
back to the host. Dashboard tile reverts to host-only.

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

internal/web/templates/dashboard.templ

@@ -9,14 +9,10 @@ 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. 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).
+// LastSeenAt is the host-mode agent's most recent heartbeat.
 type TileData struct {
 	Host             model.Host
 	Latest           *model.Run
-	Stages           []model.Stage
 	SpecDiffCritical int
 	HoldKeyPath      string
 	LastSeenAt       *time.Time