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, 26 insertions, 10 deletions

diff --git a/packages/meshbay-node/tests/test_chat_store.py b/packages/meshbay-node/tests/test_chat_store.py
index 2533921..c4dff6d 100644
--- a/packages/meshbay-node/tests/test_chat_store.py
+++ b/packages/meshbay-node/tests/test_chat_store.py
@@ -28,7 +28,6 @@ async def test_save_and_retrieve(store):
     assert msgs[0].sender_id == "alice"
     assert msgs[0].iteration == 0
     assert msgs[0].payload == b"hello"
-    assert msgs[0].thread_id is None
 
 
 @pytest.mark.asyncio
@@ -52,15 +51,32 @@ async def test_get_messages_since(store):
 
 
 @pytest.mark.asyncio
-async def test_thread_messages(store):
-    await store.save_message("alice", 0, b"root", thread_id="t1")
-    await store.save_message("bob", 1, b"reply", thread_id="t1")
-    await store.save_message("carol", 2, b"other")
-
-    thread = await store.get_thread("t1")
-    assert len(thread) == 2
-    assert thread[0].sender_id == "alice"
-    assert thread[1].sender_id == "bob"
+async def test_the_thread_column_stays_for_an_older_node_and_its_index_goes(tmp_path):
+    """Chat has no threads; a node downgraded to a version that still names
+    `thread_id` in every query must keep reading its rows."""
+    import sqlite3
+    path = tmp_path / "chat.db"
+    with sqlite3.connect(path) as c:                 # as an older node left it
+        c.executescript("""
+            CREATE TABLE messages (id INTEGER PRIMARY KEY AUTOINCREMENT,
+                sender_id TEXT NOT NULL, iteration INTEGER NOT NULL,
+                payload BLOB NOT NULL, timestamp REAL NOT NULL,
+                thread_id TEXT DEFAULT NULL, sender_name TEXT DEFAULT '');
+            CREATE INDEX idx_messages_thread ON messages(thread_id);
+            INSERT INTO messages (sender_id, iteration, payload, timestamp, thread_id)
+                VALUES ('alice', 0, X'6869', 1.0, 't1');""")
+    s = ChatStore(path)
+    await s.open()
+    await s.save_message("bob", 1, b"now")
+    assert [m.payload for m in await s.get_recent()] == [b"hi", b"now"]
+    await s.close()
+    with sqlite3.connect(path) as c:
+        assert "thread_id" in [r[1] for r in c.execute("PRAGMA table_info(messages)")]
+        assert not c.execute("SELECT 1 FROM sqlite_master WHERE name = "
+                             "'idx_messages_thread'").fetchone()
+        # What an older node selects still answers.
+        assert c.execute("SELECT thread_id FROM messages ORDER BY id").fetchall() == [
+            ("t1",), (None,)]
 
 
 @pytest.mark.asyncio