MAINT: Test and clarify timing precision accessors

[lntutor]

Summary

• add isolated coverage for timing precision reads, updates, and validation errors
• clarify get_default_precision() as the read-only equivalent of float_precision()
• replace uncollected doctest-style prompts with regular usage guidance
• clean existing whitespace violations in the timing module

Closes #889

Validation

• uv run --extra testing pytest quantecon/tests/test_timings.py -q
• uv run --extra testing flake8 quantecon/timings quantecon/tests/test_timings.py

I also started the full pytest quantecon -q suite; it ran cleanly through 47% before the local terminal session ended unexpectedly.

[quantecon-services]

Hi @lntutor, thank you for picking this up and for engaging with all three parts of #889 rather than just the tests. You were the first to claim the issue, and your reading of the accessor duplication and the never-run doctest example was correct.

I am closing this PR, but not because the work was poor. The reason is a mistake in the issue itself: the audit checked for a test directory under quantecon/timings/ and missed that the module is already fully covered by TestGlobalPrecision in quantecon/util/tests/test_timing.py (get, set, all three ValueError paths, state restoration). So the test half of this PR duplicated coverage that already existed. The >>>-absence assertion also would not survive #920, which is moving the project toward running docstring examples rather than removing them.

The docstring half was the valuable part, and I have carried it forward in #959 with credit to you: it documents get_default_precision() as the read-only equivalent of float_precision(), repairs the one example line that fails under strict doctest (keeping the >>> form so #920 can execute it), and picks up your whitespace and end-of-file fixes. I hope that is an acceptable outcome; please say if you would rather rework this PR to that scope yourself and I will close #959 instead.

I have also closed #889 with a note about what went wrong. If you would like another issue, the 2026-07 Technical Debt Audit milestone has plenty, and I would be happy to review.

Thanks again, and apologies for the wasted effort on the test side.

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