feat(web): redesign task rail — Plan/Event log polish, entity graph resize fix

- Plan/Activity panels: humanize step titles, richer icons, empty states
  matching Scope's illustration style, pretty-printed expandable detail
- Activity log renamed to Event log; every step now expandable
- Chat: middle-truncate header title, remove redundant task-list rail and
  header stat cluster (duplicated in the sidebar), simplify markdown styling
- Fix --font-mono actually being a monospace font (was aliased to DM Sans)
- Replace rotating loader-circle spinner with a smoother fading-blade Spinner
- SessionGraph entity detail panel: resizable and self-clamping against its
  live container size (was overflowing into sibling sections), close button
- Dev launch config: fetch bearer token from the running api container so
  `npm run dev` works against the local compose stack without a hardcoded
  secret in a tracked file

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

web/index.html

@@ -6,7 +6,7 @@
     <title>Oikos</title>
     <link rel="preconnect" href="https://fonts.googleapis.com" />
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
-    <link href="https://fonts.googleapis.com/css2?family=DM+Sans:ital,opsz,wght@0,9..40,100..1000;1,9..40,100..1000&family=Inknut+Antiqua:wght@300;400;500;600;700&display=swap" rel="stylesheet" />
+    <link href="https://fonts.googleapis.com/css2?family=DM+Sans:ital,opsz,wght@0,9..40,100..1000;1,9..40,100..1000&family=DM+Mono:ital,wght@0,300;0,400;0,500;1,300;1,400;1,500&family=Inknut+Antiqua:wght@300;400;500;600;700&display=swap" rel="stylesheet" />
     <link rel="icon" type="image/svg+xml" href="favicon.svg" />
     <link rel="apple-touch-icon" href="apple-touch-icon.png" />
     <link rel="icon" type="image/png" sizes="192x192" href="android-chrome-192.png" />