[sylvesterkaczmarek]

Fixes #286.

Changes

• Avoid converting an infinite or NaN insert-sample window to an integer in _disable_insert_blocking.
• Preserve the existing midpoint behavior for bounded rate limiters.
• For an unbounded window, use the table's min_size_to_sample (at least one) when checking if the learner has enough replay items.
• Add six parameterized regression cases for bounded, empty, infinite, NaN, and overflowed balance windows, with Reverb objects mocked.

Validation

• A local isolated harness executed the exact updated function from source with fake Reverb objects across 8 scenarios, all passing. Full Acme integration tests were not run because the Reverb/TensorFlow runtime was unavailable locally.
• python -m compileall on both changed files: passed.
• ruff check --select E4,E7,E9,F on both changed files: passed.
• git diff --check: passed.

The upstream CI and maintainers still need to validate the new tests in the complete runtime.