concurrent.interpreters.Queue.get()/put() mishandle the timeout argument

concurrent.interpreters.Queue.get() and Queue.put() mishandle their
timeout argument in three related ways.

1. The value is converted with int(timeout), which truncates a floating-point
   timeout to whole seconds. A timeout in the interval [0, 1) becomes a
   non-blocking call, and e.g. timeout=1.9 waits for only about one second.
   queue.Queue, which this queue is meant to be compatible with, accepts a
   floating-point number of seconds.

2. Because of the same int() conversion, a small negative float such as
   timeout=-0.5 is truncated to 0 and passes the timeout < 0 check
   instead of raising ValueError.

3. The deadline is computed with time.time() (the wall clock), while
   queue.Queue uses time.monotonic(). The timeout can therefore over- or
   under-wait if the system clock is adjusted (NTP step, manual change) during
   the call.

Reproducer (3.14.5)

import time
from concurrent.interpreters import create_queue

q = create_queue(maxsize=1)
q.put(b"x")                      # fill it
start = time.perf_counter()
try:
    q.put(b"y", timeout=0.5)     # expected: block ~0.5s, then QueueFull
except Exception as exc:
    print(type(exc).__name__, f"{(time.perf_counter() - start) * 1000:.1f} ms")
# -> QueueFull 0.0 ms   (expected ~500 ms)

q2 = create_queue()
start = time.perf_counter()
try:
    q2.get(timeout=0.9)          # expected: block ~0.9s, then QueueEmpty
except Exception as exc:
    print(type(exc).__name__, f"{(time.perf_counter() - start) * 1000:.1f} ms")
# -> QueueEmpty 0.0 ms  (expected ~900 ms)

For comparison, queue.Queue().get(timeout=0.5) blocks for about 500 ms.

The fix is to use the timeout value as given, reject a negative or NaN timeout
with ValueError, and base the deadline on time.monotonic().

Linked PRs

• gh-153006
• gh-154156
• gh-155967
• gh-156018
• gh-156019

Start with concurrent.interpreters.Queue.get() and Queue.put(), then compare their timeout handling with queue.Queue as described in the issue. Confirm the behavior for fractional, negative, and NaN timeouts and for clock adjustments; done means preserving fractional waits, raising ValueError where specified, and using a monotonic deadline. Inspect the linked PRs before starting because work is already underway.