feat: master-detail entity sheet, freshness in Entities table, live logo

Problem: the web UI felt dead and hard to navigate — the Entities table
had no health/freshness signal (just a meaningless row-mutation
timestamp), no way to see what was actually monitoring an entity,
sessions couldn't be reopened, and every drill-down was a full page
navigation that lost the list.

Change:
- Entities table: Updated column replaced with a health dot + relative
  "checked Xm ago", sourced from the backend's new health/last_check_at
  fields.
- New EntityDetailContent.svelte extracted from EntityDetail.svelte and
  shared between the full #/entity/:slug page and a new EntitySheet.svelte
  opened from the Entities table (master-detail, row click opens a panel
  instead of navigating away). Adds a Monitoring card listing the
  entity's check_defs (kind, interval, enabled/disabled with
  click-to-toggle via the existing PatchCheck endpoint) and renders
  attributes as key/value pairs instead of raw JSON.
- Sessions: fixed a bug where clicking a session loaded it into the
  chat store but never navigated to the chat page, so nothing appeared
  to happen. Added a SessionRail inside Chat so switching sessions
  never leaves the chat surface.
- Fixed the local dev proxy (vite.config.ts): production Caddy strips
  the /agent prefix before forwarding to nomos; the dev proxy didn't,
  so every session/chat fetch 404'd locally while working in prod.
- Found and fixed a real latent bug while testing the session fix:
  chat.ts's loadSessionMessages passed the persisted tool_calls array
  straight through, but nomos stores the tool_use and tool_result as
  two entries sharing one id. Chat.svelte's keyed {#each tool (tool.id)}
  throws on the duplicate key, which silently blanked the entire
  message list — invisible until sessions were actually clickable.
  Fixed by merging tool_calls by id before rendering, matching the
  shape the live-streaming path already produces.
- UI polish: sidebar logo is now just the omicron mark in white (was
  icon+text in the accent color); removed the sheet overlay's
  backdrop-blur (distracting per feedback); the Attributes/Relations/
  Signals grids used viewport-based lg:/3xl: breakpoints, which forced
  multi-column layouts based on browser width regardless of the sheet's
  actual rendered width — switched to Tailwind v4 container queries
  (@lg:/@2xl:/@3xl:) so layout responds to the real available width in
  both the full page and the narrower sheet.

Risk: reversible_low (UI-only; no destructive operations; the tool_calls
merge and dev-proxy fix are corrections to broken paths, not behavior
changes to working ones).

Verification: npx tsc --noEmit clean (excluding pre-existing unrelated
.svelte type-resolution warnings). Manually verified in the browser
preview against the live dev API: Entities table health column renders
correctly; clicking a row opens the EntitySheet with a populated
Monitoring card (16 checks for host:hubris, verified via psql that
check_defs.target_id links them correctly); clicking a session now
loads its full transcript inline (was blank before the tool_calls fix);
sheet has no blur and lays out single/multi-column correctly at the
sheet's actual width.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/pages/Entities.svelte

@@ -1,12 +1,22 @@
 <script lang="ts">
   import { onMount } from 'svelte'
-  import { fetchEntities, type Entity } from '$lib/api'
+  import { fetchEntities, type Entity, type EntityHealth } from '$lib/api'
   import { liveEvents, subscribeEvents } from '$lib/stores/events'
+  import { relativeTime } from '$lib/utils'
   import * as Table from '$lib/components/ui/table'
   import { Badge } from '$lib/components/ui/badge'
   import { Input } from '$lib/components/ui/input'
   import * as Select from '$lib/components/ui/select'
   import { Skeleton } from '$lib/components/ui/skeleton'
+  import EntitySheet from '$lib/components/EntitySheet.svelte'
+
+  let sheetOpen = $state(false)
+  let selectedSlug = $state<string | null>(null)
+
+  function openEntity(slug: string) {
+    selectedSlug = slug
+    sheetOpen = true
+  }
 
   let entities = $state<Entity[]>([])
   let loading = $state(true)
@@ -47,6 +57,20 @@
     if (state === 'active' || state === 'healthy') return 'default'
     return 'secondary'
   }
+
+  const healthDot: Record<EntityHealth, string> = {
+    healthy: 'bg-success',
+    degraded: 'bg-warning',
+    down: 'bg-destructive',
+    stale: 'bg-warning/50',
+    unknown: 'bg-muted-foreground/40'
+  }
+
+  function healthTitle(entity: Entity): string {
+    if (!entity.health) return 'not monitored'
+    if (entity.health === 'stale') return `stale — last checked ${relativeTime(entity.last_check_at)}`
+    return `${entity.health} — checked ${relativeTime(entity.last_check_at)}`
+  }
 </script>
 
 <div class="flex h-full flex-col gap-4 p-6">
@@ -85,14 +109,14 @@
             <Table.Head>Type</Table.Head>
             <Table.Head>Name</Table.Head>
             <Table.Head>State</Table.Head>
-            <Table.Head>Updated</Table.Head>
+            <Table.Head>Health</Table.Head>
           </Table.Row>
         </Table.Header>
         <Table.Body>
           {#each filtered as entity (entity.id)}
             <Table.Row
               class="cursor-pointer"
-              onclick={() => (location.hash = '#/entity/' + encodeURIComponent(entity.slug))}
+              onclick={() => openEntity(entity.slug)}
             >
               <Table.Cell class="font-mono text-xs">{entity.slug}</Table.Cell>
               <Table.Cell><Badge variant="outline">{entity.type}</Badge></Table.Cell>
@@ -104,9 +128,16 @@
                   <span class="text-muted-foreground">—</span>
                 {/if}
               </Table.Cell>
-              <Table.Cell class="text-xs text-muted-foreground"
-                >{new Date(entity.updated_at).toLocaleString()}</Table.Cell
-              >
+              <Table.Cell>
+                {#if entity.health}
+                  <span class="flex items-center gap-1.5 text-xs" title={healthTitle(entity)}>
+                    <span class="size-2 shrink-0 rounded-full {healthDot[entity.health]}"></span>
+                    <span class="text-muted-foreground">{relativeTime(entity.last_check_at)}</span>
+                  </span>
+                {:else}
+                  <span class="text-xs text-muted-foreground">—</span>
+                {/if}
+              </Table.Cell>
             </Table.Row>
           {:else}
             <Table.Row>
@@ -120,3 +151,5 @@
     </div>
   {/if}
 </div>
+
+<EntitySheet slug={selectedSlug} bind:open={sheetOpen} />