The cursor I/O loop previously treated any wire failure as terminal —
first disconnect = sender broken, every subsequent batch threw. Now,
when the sender wires a ReconnectFactory + ReconnectListener, a wire
failure triggers:

  1. WARN log
  2. Build a fresh WebSocketClient via the factory (same auth/TLS/host)
  3. Reset wire state: nextWireSeq=0, fsnAtZero = engine.ackedFsn() + 1
  4. Reposition the cursor at the first unacked FSN (replay)
  5. Notify the listener → producer's connectionGeneration bumps so
     the next encode emits full schema definitions, not refs the new
     server has never seen
  6. Outer ioLoop continues — nextWireSeq=0 starts on the new wire,
     trySendOne picks up at the repositioned cursor and replays every
     unacked frame, then continues with whatever the producer publishes
     next

Added in main:
  * CursorWebSocketSendLoop.ReconnectFactory + .ReconnectListener
    interfaces (both functional, both null-able for legacy "fail-fast"
    semantics)
  * positionCursorAt(fsn) — walks frames inside the segment containing
    fsn to find the byte offset
  * SegmentRing.findSegmentContaining(fsn) + CursorSendEngine
    pass-through — used by the cursor reposition
  * QwpWebSocketSender extracts buildAndConnect() to use both for the
    initial connect and as the reconnect factory; onWireReconnect()
    is the listener that bumps connectionGeneration

This commit covers the *mechanics* (one attempt, succeed-or-fail).
The follow-up commit adds policy: exponential backoff with jitter,
per-outage time cap (reconnect_max_duration_millis, default 300s
per spec decision #2), and auth-failure detection (401/403/non-101
treated as terminal so the retry budget isn't wasted on errors that
won't fix themselves).

Two integration tests:
  * testReconnectAfterServerInducedDisconnect — server ACKs then
    closes; sender reconnects, second batch lands on the new wire
  * testReplayResendsUnackedFramesAcrossReconnect — server receives
    the first frame WITHOUT ACKing then closes; sender reconnects
    and replays the unacked frame on the new connection

Spec decisions #5 (encode-mid-reconnect race) and the core of
#1/#2 (reconnect mechanics) land here.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>