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/api/tile.go

@@ -19,7 +19,6 @@ 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
 }
@@ -54,16 +53,6 @@ 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
 }