@Retryable against a permanently-dead downstream: two consecutive calls, no shared state
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-- Call 1: pay("order-A") --
threw FlakyDownstream.DownstreamUnavailableException after exhausting retries
downstream calls so far: 4  (1 initial attempt + 3 retries = 4 expected)

-- Call 2: pay("order-B"), immediately after Call 1 exhausted its retries --
downstream calls so far: 8  (another 4 attempts, not fast-failed)

Contrast with docs/output/01-circuitbreaker-trip.txt: there, calls 7-9 after the trip
added ZERO downstream calls. Here, call 2 pays the same 4-attempt cost as call 1.
@Retryable has no OPEN state -- it cannot tell you 'this dependency is currently down'.