chore: fix preview routes, MarkdownRenderer, update opencode config

- _preview_routes.py: fix preview endpoint params for multi-language
- MarkdownRenderer.svelte: renderer fixes for assistant messages
- speckit.analyze.md: update opencode command for spec analysis
- opencode.jsonc: config alignment

frontend/src/lib/components/assistant/MarkdownRenderer.svelte

@@ -1,12 +1,12 @@
 <!-- #region AssistantChat.MarkdownRenderer [C:2] [TYPE Component] [SEMANTICS assistant,chat,markdown,rendering] -->
 <!-- @ingroup AgentChat -->
-<!-- @BRIEF Renders markdown text using svelte-markdown with semantic Tailwind prose styles. -->
+<!-- @BRIEF Renders markdown text using @humanspeak/svelte-markdown with semantic Tailwind prose styles. -->
 <!-- @LAYER UI -->
-<!-- @RELATION DEPENDS_ON -> [EXT:svelte-markdown] -->
+<!-- @RELATION DEPENDS_ON -> [EXT:@humanspeak/svelte-markdown] -->
 <!-- @UX_STATE Rendered -> Markdown rendered with proper headings, lists, code blocks, links. -->
 <!-- @UX_STATE Empty -> Empty string renders nothing. -->
 <script lang="ts">
-  import SvelteMarkdown from "svelte-markdown";
+  import SvelteMarkdown from "@humanspeak/svelte-markdown";
 
   let { source = "" } = $props();
 </script>
@@ -18,7 +18,7 @@
 {/if}
 
 <style>
-  /* svelte-markdown renderers use semantic HTML tags — style via cascade */
+  /* @humanspeak/svelte-markdown renderers use semantic HTML tags — style via cascade */
   .markdown-text :global(h1),
   .markdown-text :global(h2),
   .markdown-text :global(h3) {