[jsonbailey]

Several fdv1 specs start a real stream or polling processor and never stop it. The leaked SSE thread later hits a 401 and calls an expired RSpec double, which shows up as a thread warning in CI. Add an after hook that stops the data source in the two describe blocks that start real processors.

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Note

Overview
Fixes flaky CI thread warnings by teardown in fdv1_spec.rb: an after { subject.stop } hook was added to the #start and diagnostic accumulator integration describe blocks.

Those examples call subject.start with real StreamProcessor / PollingProcessor instances, which left background SSE threads running after the example finished. Those threads could later get a 401 and touch expired RSpec doubles. Stopping the data source after each example keeps processor threads from outliving the test.

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