* tests: add SMP proxy relay reconnection tests
Reproduces the proxy failing to reconnect to a destination relay when the
sender disconnects mid-connection (empty session var left in smpClients).
* fix: bracket session var creation to drop it on interrupt
getSessVar inserts an empty session var that the connect path then fills with
putTMVar. If the connecting thread is killed by an async exception before that
fill (a proxy worker on client disconnect, an agent worker on cancel), the empty
var was left in the map forever and every later request for that server blocked
on it until timing out (permanent PCEResponseTimeout).
Wrap get-or-create with withGetSessVar (bracketOnError) at the call sites, so the
cleanup is established where the var is created and covers the whole connect: on
interrupt before fill the still-empty var is dropped and the next request
reconnects. This closes the window between getSessVar and the fill that a handler
installed inside the connect function cannot cover.
* test: cover session var leak on interrupted connect
UtilTests: tryAllErrors rethrows ThreadKilled/StackOverflow (the mechanism
that skips putTMVar). SMPProxyTests: agent client reconnection after a
cancelled connect, plus a control proving the stalling relay alone does not
cause the failure; refine the relay reconnection tests.
* refactor
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Co-authored-by: Evgeny Poberezkin <evgeny@poberezkin.com>
* agent: catch IO errors correctly in MonadError
* correction
* correction
* utils
* agentFinally to catch IO exceptions in ExceptT
* rename
* remove, inline
* rename utils
* utils unit test
* test to show catch and finally problems
* tryAllErrors
* enable all tests
