Issue #6 and the Go sample it was ported from predate Workflow Update. Per
maintainer feedback, replace the response-activity port with an update-based
sample: the update handler runs the uppercase activity and returns the result
to the caller, removing the response task queue, the callback activity and the
request IDs.

Ports the durability parts of samples-go/reqrespupdate: a request counter,
continue-as-new to bound history, and an update validator that rejects requests
while a run drains so the requester backs off and retries against the fresh run.

Uses workflow.all_handlers_finished() for the drain rather than Go's hand-rolled
pending counter, matching message_passing/safe_message_handlers.
message_passing/waiting_for_handlers notes the continue-as-new drain case is not
illustrated there, so this sample covers it.

Adds tests, which the original sample did not have.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

The tests were skipping when env.supports_time_skipping, on the assumption
that the Java test server does not support workflow update. It does: both
tests pass against it, repeatedly. CI runs the suite twice, once per
environment, so the guard was halving this sample's coverage for no reason.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

- Bound the test retry helper with a max attempt count and a short sleep, so
  a workflow that stops continuing as new fails the test instead of retrying
  forever and hanging CI.
- Skip both tests on the time-skipping server, matching the other update
  tests in the repo (temporalio/sdk-java#1903).
- Reject requests_before_continue_as_new < 1 in the workflow constructor.
  Zero made the run continue as new immediately and forever while rejecting
  every request.
- Move TASK_QUEUE and WORKFLOW_ID into __init__.py, as sleep_for_days and
  message_passing/waiting_for_handlers do, instead of the worker hardcoding
  the task queue name.
- Use the existing handle in the continue-as-new test rather than re-fetching
  it; start_workflow does not pin the handle to a run.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

# Conflicts:
#	pyproject.toml