commands/e2e: drop topologyVersion from the handshake; rename to mongo-lite

Advertising topologyVersion in the hello reply is what tells a driver the
server speaks the streaming (awaitable) hello protocol — in the Node driver
it is the only condition checked. From the second heartbeat on, the driver
then monitored with an exhaust hello (exhaustAllowed + maxAwaitTimeMS) and
waited for a stream of replies carrying moreToCome. We answered once with
the flag clear and went back to reading, so every heartbeat failed with
"Server ended moreToCome unexpectedly", destroying the connection and
clearing the pool. MongoDB Compass showed this as a connect/disconnect loop
once per heartbeat.

We do not implement streaming hello, so we must not claim to. Omitting the
field keeps monitoring on the polling path, and agrees with the
maxWireVersion 8 we report: streaming hello arrived in wire version 9.

The existing e2e files all passed against the broken server — they issue
their commands and exit before the second heartbeat — so e2e5 watches SDAM
heartbeats on an idle connection instead.

Also renames mongo-light to mongo-lite throughout (binary, log messages,
docs, gitVersion). Unrelated to the fix above, but squashed in at request
rather than left as a commit whose message described only the fix.

README.md

@@ -1,4 +1,4 @@
-# mongo-light
+# mongo-lite
 
 A lightweight, embedded MongoDB-compatible document database written in
 Zig 0.16. Like SQLite, it stores everything in a single file; unlike SQLite,
@@ -11,7 +11,7 @@ driver, PyMongo — connect over TCP and just work.
 zig build                # build the server
 zig build test           # run the unit test suite
 
-zig-out/bin/mongo-light --port 27017 --db data.log
+zig-out/bin/mongo-lite --port 27017 --db data.log
 
 # in another terminal:
 mongosh --port 27017