fix(ws-server): don't apply a gapped changeset after rejecting it

[silviot]

Bug

InboundStream.receiveChanges (server) detects a gap — the incoming changeset's since is ahead of
the version we have actually applied (#lastSeen) — and sends RejectChanges, but there is no
return. It falls through and applies the non-contiguous batch anyway, then advances #lastSeen
and the durable crsql_tracked_peers cursor past the gap.

The server then believes it has received everything from that peer and never re-requests the
missing range, so the peer's committed changes are silently and permanently lost on the server and
on every other peer — "converged but not actually synced" divergence. This is the inbound/apply twin
of the OutboundStream.reset() stub that was fixed in the outbound direction.

The client's InboundStream already does the right thing: it returns immediately after rejecting
(and reverts #lastSeens on apply failure).

This was reproduced against the shipped @vlcn.io/ws-server artefact (vlcn.io-ws-server-0.2.2):
a gapped changeset is applied (applied.length === 1) while a reject is also sent.

Fix

return; after rejectChanges. The server keeps #lastSeen at the pre-gap value, so the missing
range is recovered when the sender re-streams from the server's last-seen (e.g. on the next
StartStreaming / reconnect).

Adds InboundStream.test.ts (mirroring OutboundStream.test.ts) covering the gapped path (rejected,
not applied) and the contiguous path (applied).

Notes / follow-ups

• This is the highest-impact half. Mid-connection recovery without a reconnect additionally requires
  the client to honour an inbound RejectChanges — today ws-client's WebSocketTransport
throws on tags.RejectChanges, so server→client gap-recovery for the upload direction is dead.
  Tracked separately.
• Targeted at librocco/main (the branch the librocco 0.2.2 tarball is built from). main has the
  same missing return and should get the same fix.
• The librocco-side regression test against the rebuilt tarball should mirror
  apps/sync-server/src/ws-server-reject-recovery.test.ts.

Co-authored-by: Claude Opus 4.8 (1M context) noreply@anthropic.com