Promote AgentCompany-New to the repository root and retire the old app

The legacy application - its src, tests, landing site, promo assets, docs,
release tooling, CI workflows, and root configs - leaves the tree; it stays
reachable in history. Everything under AgentCompany-New moves up unchanged:
same package name, so the production userData/database path is untouched,
and e2e/build scripts already resolved paths relative to the project. The
developer cred.txt stays gitignored at its new location. Full verify:ci
passes from the new root.

src/main/services/agent-message-presence.ts

@@ -0,0 +1,83 @@
+import type { DatabaseSync } from "node:sqlite";
+
+/**
+ * What the sending agent hears back: who is in the channel and who they just
+ * addressed — the presence of real colleagues, not a transaction id. Hearing
+ * the room is what lets an agent hold a conversation instead of posting into a
+ * void, while the thread_id keeps the next reply on the same thread.
+ */
+export function describeSend(db: DatabaseSync, selfAgentId: string, channel: string, spaceId: string, messageId: string, threadId: string): string {
+  const addressed = mentionedTeammates(db, selfAgentId, messageId);
+  const present = channelTeammates(db, selfAgentId, spaceId, addressed);
+  const lines = [`Your message is up in #${channel}.`];
+  const replyReady = addressed.filter((teammate) => teammate.canReply).map((teammate) => teammate.name);
+  const mentionedOnly = addressed.filter((teammate) => !teammate.canReply).map((teammate) => teammate.name);
+  if (replyReady.length > 0) lines.push(`${joinNames(replyReady)} can see it and reply here.`);
+  if (mentionedOnly.length > 0) lines.push(`${joinNames(mentionedOnly)} was mentioned in this thread.`);
+  if (present.length > 0) lines.push(`Also in the room: ${joinNames(present)}.`);
+  lines.push(`To stay in this conversation, reply with thread_id="${threadId}".`);
+  return lines.join(" ");
+}
+
+interface MentionedTeammate {
+  name: string;
+  canReply: boolean;
+}
+
+function mentionedTeammates(db: DatabaseSync, selfAgentId: string, messageId: string): MentionedTeammate[] {
+  const wakePattern = `%"sourceMessageId":"${messageId}"%`;
+  const rows = db.prepare(`
+    select coalesce(a.name, e.display_name) as name,
+           case
+             when m.target_type = 'employee' then 1
+             when exists (
+               select 1
+               from task_runs r
+               where r.agent_id = m.target_id
+                 and r.trigger = 'chat_mention'
+                 and r.secret_scope_json like ?
+             ) then 1
+             else 0
+           end as can_reply
+    from chat_mentions m
+    left join agents a on a.id = m.target_id and m.target_type = 'agent'
+    left join employees e on e.id = m.target_id and m.target_type = 'employee'
+    where m.message_id = ? and m.target_type in ('agent', 'employee') and m.target_id <> ?
+  `).all(wakePattern, messageId, selfAgentId) as Array<{ name: string | null; can_reply: number }>;
+  return dedupeTeammates(rows);
+}
+
+function channelTeammates(db: DatabaseSync, selfAgentId: string, spaceId: string, addressed: MentionedTeammate[]): string[] {
+  const alreadyNamed = new Set(addressed.map((teammate) => teammate.name));
+  const rows = db.prepare(`
+    select coalesce(a.name, e.display_name) as name
+    from chat_memberships cm
+    left join agents a on a.id = cm.principal_id and cm.principal_type = 'agent'
+    left join employees e on e.id = cm.principal_id and cm.principal_type = 'employee'
+    where cm.space_id = ? and cm.principal_id <> ?
+  `).all(spaceId, selfAgentId) as Array<{ name: string | null }>;
+  return dedupeNames(rows).filter((name) => !alreadyNamed.has(name)).slice(0, 6);
+}
+
+function dedupeNames(rows: Array<{ name: string | null }>): string[] {
+  const names = new Set<string>();
+  for (const row of rows) if (row.name) names.add(row.name);
+  return [...names];
+}
+
+function dedupeTeammates(rows: Array<{ name: string | null; can_reply: number }>): MentionedTeammate[] {
+  const teammates = new Map<string, MentionedTeammate>();
+  for (const row of rows) {
+    if (!row.name) continue;
+    const existing = teammates.get(row.name);
+    const canReply = row.can_reply === 1;
+    teammates.set(row.name, { name: row.name, canReply: canReply || existing?.canReply === true });
+  }
+  return [...teammates.values()];
+}
+
+function joinNames(names: string[]): string {
+  if (names.length === 1) return names[0];
+  if (names.length === 2) return `${names[0]} and ${names[1]}`;
+  return `${names.slice(0, -1).join(", ")}, and ${names[names.length - 1]}`;
+}