refactor(chat): no thread_id — chat has no threads

Nothing ever set it (the page and the CLI sent null) and nothing read it
(the node's get_thread had no caller). It is no longer sent by the page or
the CLI, in clear or in the sealed payload, nor relayed or served by the
node; get_thread and its index are gone, and the protocol and design docs
no longer name it.

The node still accepts a chat_msg carrying one, from the desktop apps and
CLIs already installed, and drops it. The column stays, empty, in chat.db:
a node downgraded to an older version names it in every query.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

2 files changed, 4 insertions, 9 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js b/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js
index 1d61c43..34e86eb 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/chat-app.js
@@ -472,7 +472,7 @@ function ChatPanel({ transportRef, username, userId, entries, gekRef,
     setSending(true);
     setInput('');
     try {
-      await transport.sendChat(text, 0, null, username);
+      await transport.sendChat(text, 0, username);
       setMessages(prev => [...prev, {
         id: `own-${Date.now()}-${Math.random().toString(36).slice(2)}`,
         own: true,
@@ -480,7 +480,6 @@ function ChatPanel({ transportRef, username, userId, entries, gekRef,
         sender_name: username,
         payload: text,
         timestamp: Date.now() / 1000,
-        thread_id: null,
       }]);
       jumpToBottom();
       if (onActivity) onActivity();
@@ -515,11 +514,11 @@ function ChatPanel({ transportRef, username, userId, entries, gekRef,
       const structured = JSON.stringify({
         text: '', attachment: { filename: storedAs, size: file.size, type: ftype },
       });
-      await transport.sendChat(structured, 0, null, username);
+      await transport.sendChat(structured, 0, username);
       setMessages(prev => [...prev, {
         id: `own-${Date.now()}-${Math.random().toString(36).slice(2)}`,
         own: true, sender_id: userId || username, sender_name: username,
-        payload: structured, timestamp: Date.now() / 1000, thread_id: null,
+        payload: structured, timestamp: Date.now() / 1000,
       }]);
       jumpToBottom();
     } catch (err) {
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport-chat.js b/packages/meshbay-hub/src/meshbay_hub/static/transport-chat.js
index 9ce07bc..3efbb22 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport-chat.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport-chat.js
@@ -138,7 +138,6 @@ extendTransport(class {
       sender_id: row.sender_id,
       sender_name: row.sender_name || '',
       timestamp: row.timestamp,
-      thread_id: row.thread_id,
     };
     const format = row.format || 0;
     if (format === 0) {
@@ -169,7 +168,7 @@ extendTransport(class {
    * post in clear into a group whose members believe their chat is encrypted;
    * the node refuses it too, and the two refusals agreeing is the point.
    */
-  async sendChat(text, iteration, threadId, senderName) {
+  async sendChat(text, iteration, senderName) {
     const keys = await this.chatKeys();
     const epoch = this.chatEpoch || keys.current;
     const epochKey = keys.byEpoch.get(epoch);
@@ -182,7 +181,6 @@ extendTransport(class {
     const gid = this._groupId || '';
     const plaintext = msgpack_encode({
       text: String(text),
-      thread_id: threadId || null,
       sender_name: senderName || '',
       sent_at: Math.floor(Date.now() / 1000),
     });
@@ -204,7 +202,6 @@ extendTransport(class {
       nonce,
       device,
       sig,
-      thread_id: threadId || null,
       // Deliberately absent: the display name is inside the envelope now.
       sender_name: null,
     });
@@ -315,7 +312,6 @@ extendTransport(class {
         ...base,
         payload: String(plain.text || ''),
         sender_name: plain.sender_name || base.sender_name,
-        thread_id: plain.thread_id ?? base.thread_id,
         device: deviceB64,
         verified: true,
         trust,