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/src/lib/components/Spinner.svelte

@@ -0,0 +1,30 @@
+<script lang="ts">
+  // A fading-blade spinner rather than a rotating arc — rotating a single
+  // thin stroke via CSS transform reads as jittery at icon sizes (the arc's
+  // sub-pixel edges shimmer each frame). Cycling opacity across fixed blades
+  // avoids that entirely and is how native OS spinners do it.
+  let { class: className = '' }: { class?: string } = $props()
+
+  const TICKS = 8
+  const DUR = 0.9
+</script>
+
+<svg viewBox="0 0 24 24" class={className} fill="none" aria-hidden="true">
+  {#each Array.from({ length: TICKS }) as _, i (i)}
+    <rect
+      x="11" y="1.5" width="2" height="6" rx="1"
+      fill="currentColor"
+      opacity="0.15"
+      transform="rotate({i * (360 / TICKS)} 12 12)"
+    >
+      <animate
+        attributeName="opacity"
+        values="1;0.15"
+        keyTimes="0;1"
+        dur="{DUR}s"
+        begin="{-(i * (DUR / TICKS)).toFixed(3)}s"
+        repeatCount="indefinite"
+      />
+    </rect>
+  {/each}
+</svg>