feat(broker+api+cli): topic message reply-to threading (v0.3.1)

Adds a reply_to_id column (self-FK on topic_message) plus end-to-end
plumbing so a message can mark itself as a reply to a previous one in
the same topic.

- Schema: 0027_topic_message_reply_to.sql adds reply_to_id with
  ON DELETE SET NULL + index for backlink lookup.
- Broker: appendTopicMessage validates parent shares the topic, writes
  reply_to_id; topicHistory + topic_history_response surface it; WS
  push envelope now carries senderMemberId, senderName, topic name,
  reply_to_id, and message_id so recipients have everything they need
  to reply without a follow-up query.
- REST: POST /v1/messages accepts replyToId (validated server-side);
  GET /messages and SSE /stream emit it per row.
- CLI: \`topic post --reply-to <id|prefix>\` resolves prefixes against
  recent history; \`topic tail\` renders an "↳ in reply to <name>:
  <snippet>" line above replies and shows a copyable #shortid tag on
  every row.
- MCP push pipe: channel attributes now include from_pubkey,
  from_member_id, message_id, topic, reply_to_id — the recipient can
  thread a reply directly from the inbound notification.
- Skill + identity prompt updated to teach Claude how to use the new
  attributes for replies.

Bumped CLI to 1.9.0.

apps/cli/src/services/broker/ws-client.ts

@@ -101,6 +101,14 @@ export interface InboundPush {
   messageId: string;
   meshId: string;
   senderPubkey: string;
+  /** Stable mesh.member id of the sender — preferred id for replies. */
+  senderMemberId?: string;
+  /** Sender's current display name (a join from the broker). */
+  senderName?: string;
+  /** Topic name when the push originated from a topic post (vs DM). */
+  topic?: string;
+  /** Server-side id of the parent message when this push is a reply. */
+  replyToId?: string;
   priority: Priority;
   nonce: string;
   ciphertext: string;
@@ -2028,6 +2036,10 @@ export class BrokerClient {
           messageId: String(msg.messageId ?? ""),
           meshId: String(msg.meshId ?? ""),
           senderPubkey,
+          ...(msg.senderMemberId ? { senderMemberId: String(msg.senderMemberId) } : {}),
+          ...(msg.senderName ? { senderName: String(msg.senderName) } : {}),
+          ...(msg.topic ? { topic: String(msg.topic) } : {}),
+          ...(msg.replyToId ? { replyToId: String(msg.replyToId) } : {}),
           priority: (msg.priority as Priority) ?? "next",
           nonce,
           ciphertext,