Review I1: ConnectAsync, DisconnectAsync and Dispose each start a new connection
epoch under _subscriptionLock. A keep-alive failover runs under the epoch it
started in and abandons itself the moment it moves: it installs its session only
if the epoch still matches (checked and assigned under the lock, otherwise the
session is disposed), its state transitions are epoch-guarded, it stops trying
endpoints, and it never flips a user's new connection to Disconnected. A late
keep-alive from a previous connection's session starts no failover. Gate-driven
tests cover the success and all-fail arms, the stale keep-alive, with a genuine
failover as the positive control (4 of them red before).
Minors: m8 only the CompareExchange winner sets LastFailover; m5 the endpoint
loop stops early, and a failed Unsubscribe still drops its bookkeeping; m1 a read
cancelled mid-paging releases its cursor (bounded token) and rethrows, and the cap
release no longer rides the caller's token; m2 results are trimmed to the cap;
m3 a non-positive cap is refused (CLI and UI already bound it to >= 1); m6 the
subscription adapter's Dispose uses one bounded bridge for delete + detach.
Refs #747
Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
Joseph Doherty
0c9e4f4e3d