Implement v0.4 subscriptions + v0.5 theming and plugin slots

- SSE and WebSocket fetchers via graphql-sse and graphql-ws,
  returning AsyncIterable results
- SessionStore.run consumes AsyncIterable streams with
  subscriptionMode "append" (timestamped) or "replace" and
  honors an AbortSignal for cancellation
- Chrome CSS variables documented in styles/theme.scss with
  prefers-color-scheme light/dark gating and .graphiql-light override
- Svelte 5 snippet slots on GraphiQL: toolbarExtras, tabExtras,
  resultFooter

1 files changed, 4 insertions, 2 deletions

diff --git a/source/library/components/TabBar.svelte b/source/library/components/TabBar.svelte
index d87449d..9c34f20 100644
--- a/source/library/components/TabBar.svelte
+++ b/source/library/components/TabBar.svelte
@@ -1,9 +1,10 @@
 <script lang="ts">
-  import { tick } from "svelte";
+  import { tick, type Snippet } from "svelte";
   import type { Tab } from "../state/session.svelte.ts";
 
   type Props = {
     activeId: string;
+    extras?: Snippet<[{ tab: Tab }]>;
     onAdd: () => void;
     onClose: (id: string) => void;
     onRename: (id: string, title: string) => void;
@@ -11,7 +12,7 @@
     tabs: Tab[];
   };
 
-  let { activeId, onAdd, onClose, onRename, onSelect, tabs }: Props = $props();
+  let { activeId, extras, onAdd, onClose, onRename, onSelect, tabs }: Props = $props();
 
   let editingId = $state<string | null>(null);
   let draft = $state<string>("");
@@ -150,6 +151,7 @@
       {:else}
         <span class="title">{tab.title}</span>
       {/if}
+      {#if extras}{@render extras({ tab })}{/if}
       <button
         aria-label="Close tab"
         class="close"