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>

1 files changed, 1 insertions, 1 deletions

diff --git a/packages/meshbay-common/tests/test_js_python_parity.py b/packages/meshbay-common/tests/test_js_python_parity.py
index bb52742..8f7f7b9 100644
--- a/packages/meshbay-common/tests/test_js_python_parity.py
+++ b/packages/meshbay-common/tests/test_js_python_parity.py
@@ -497,7 +497,7 @@ const toHex = (u8) =>
 
 def _chat_payload(idx: int) -> dict:
     """A distinct message per vector, so a crossed result cannot pass."""
-    return {"text": f"message {idx} — café", "thread_id": None,
+    return {"text": f"message {idx} — café",
             "sender_name": f"member-{idx}", "sent_at": 1_700_000_000 + idx}