feat(mentions): support @all to mention all workspace members

Add @all mention type that notifies all workspace members (excluding
agents). Includes backend parsing, notification expansion to all members,
and frontend UI with autocomplete suggestion, rendering, and hover card.

apps/web/components/common/mention-hover-card.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import type { ReactNode } from "react";
+import { Users } from "lucide-react";
 import { HoverCard, HoverCardTrigger, HoverCardContent } from "@/components/ui/hover-card";
 import { ActorAvatar } from "@/components/common/actor-avatar";
 import { useWorkspaceStore } from "@/features/workspace";
@@ -15,6 +16,27 @@ function MentionHoverCard({ type, id, children }: MentionHoverCardProps) {
   const members = useWorkspaceStore((s) => s.members);
   const agents = useWorkspaceStore((s) => s.agents);
 
+  if (type === "all") {
+    return (
+      <HoverCard>
+        <HoverCardTrigger render={<span />} className="cursor-default">
+          {children}
+        </HoverCardTrigger>
+        <HoverCardContent align="start" className="w-auto min-w-48 max-w-72">
+          <div className="flex items-center gap-2.5">
+            <div className="flex h-8 w-8 shrink-0 items-center justify-center rounded-full bg-primary/10">
+              <Users className="h-4 w-4 text-primary" />
+            </div>
+            <div className="min-w-0">
+              <p className="text-sm font-medium">All members</p>
+              <p className="text-xs text-muted-foreground">Notifies all workspace members</p>
+            </div>
+          </div>
+        </HoverCardContent>
+      </HoverCard>
+    );
+  }
+
   if (type === "member") {
     const member = members.find((m) => m.user_id === id);
     if (!member) return <>{children}</>;

apps/web/components/common/mention-suggestion.tsx

@@ -8,7 +8,7 @@ import {
   useRef,
   useState,
 } from "react";
-import { Hash } from "lucide-react";
+import { Hash, Users } from "lucide-react";
 import { ReactRenderer } from "@tiptap/react";
 import { computePosition, offset, flip, shift } from "@floating-ui/dom";
 import { useWorkspaceStore } from "@/features/workspace";
@@ -23,7 +23,7 @@ import type { SuggestionOptions, SuggestionProps } from "@tiptap/suggestion";
 export interface MentionItem {
   id: string;
   label: string;
-  type: "member" | "agent" | "issue";
+  type: "member" | "agent" | "issue" | "all";
   /** Secondary text shown below the label (e.g. issue title) */
   description?: string;
 }
@@ -99,7 +99,11 @@ const MentionList = forwardRef<MentionListRef, MentionListProps>(
             }`}
             onClick={() => selectItem(index)}
           >
-            {item.type === "issue" ? (
+            {item.type === "all" ? (
+              <span className="inline-flex h-5 w-5 shrink-0 items-center justify-center rounded-full bg-primary/10 text-primary">
+                <Users className="h-3 w-3" />
+              </span>
+            ) : item.type === "issue" ? (
               <span className="inline-flex h-5 w-5 shrink-0 items-center justify-center rounded-full bg-primary/10 text-primary">
                 <Hash className="h-3 w-3" />
               </span>
@@ -137,6 +141,12 @@ export function createMentionSuggestion(): Omit<
       const { issues } = useIssueStore.getState();
       const q = query.toLowerCase();
 
+      // Show "All members" option when query is empty or matches "all"
+      const allItem: MentionItem[] =
+        "all members".includes(q) || "all".includes(q)
+          ? [{ id: "all", label: "All members", type: "all" as const, description: "Notify all members" }]
+          : [];
+
       const memberItems: MentionItem[] = members
         .filter((m) => m.name.toLowerCase().includes(q))
         .map((m) => ({
@@ -162,7 +172,7 @@ export function createMentionSuggestion(): Omit<
           description: i.title,
         }));
 
-      return [...memberItems, ...agentItems, ...issueItems].slice(0, 10);
+      return [...allItem, ...memberItems, ...agentItems, ...issueItems].slice(0, 10);
     },
 
     render: () => {

apps/web/components/common/rich-text-editor.tsx

@@ -103,7 +103,7 @@ const MentionExtension = Mention.configure({
       return {
         type: "mention",
         raw: match[0],
-        attributes: { label: match[1], type: match[2], id: match[3] },
+        attributes: { label: match[1], type: match[2] ?? "member", id: match[3] },
       };
     },
   },