The cache-miss isAgentUnreachable check added in #24336 runs before
dialWithLazyValidation, preventing the existing switch mechanism from
discovering the new agent after a workspace rebuild. The chat's stale
agent binding is never repaired, causing an infinite loop of
'agent is disconnected' errors.
Remove the cache-miss check. The cache-hit check remains (it verifies
the agent behind an established connection). The dial timeout and
dialWithLazyValidation already bound the cache-miss failure path.
Closes CODAGT-248