feat(group-chat): add @all mention routing (#857)

Add modular group-chat mention routing helpers for the reserved @all token, route it to every non-sender agent, and strip routing tokens before model input.

Expose @all in mention autocomplete, highlight it in group messages, reserve literal all agent names, and cover boundary/partial-match regressions with tests.

packages/client/src/components/hermes/chat/MarkdownRenderer.vue

@@ -137,8 +137,10 @@ const renderedHtml = computed(() => {
   })
 
   if (props.mentionNames && props.mentionNames.length > 0) {
-    const escaped = props.mentionNames.map(n => n.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'))
-    const re = new RegExp(`(?<=[\\s>]|^)@(${escaped.join('|')})(?=\\s|$)`, 'gi')
+    const escaped = [...props.mentionNames]
+      .sort((a, b) => b.length - a.length)
+      .map(n => n.replace(/[.*+?^${}()|[\]\\]/g, '\\$&'))
+    const re = new RegExp(`(?<=[\\s>({\\[<]|^)@(${escaped.join('|')})(?=[\\s.,!?;:，。！？；：)\\]}>]|<|$)`, 'gi')
     html = html.replace(re, '<span class="mention-highlight">@$1</span>')
   }
   return html