Prepare Python 2.5.15 query authority without regressing backfill docs

[rmcdaniel]

Compatible 2.5.15 preparation

Refs #143 and #152. Version 2.5.14 was already published for the backfill documentation correction. Its tag/package remain unchanged; the query candidate has never been published.

This follow-up prepares 2.5.15 and merges the genuine published 2.5.14 source into the query maintenance branch. It preserves that release's backfill docstring, reference page and changelog. Relative to the qualified query candidate, executable query logic is unchanged: the Client source difference is its restored backfill docstring, plus version/docs metadata. Pending main/Nexus behavior is excluded.

The query implementation retains the original non-renewing loading/replay/handler budget, same-response reference reuse, optional strong pre-registration requirement and explicit legacy/1.19 limits. The asynchronous versus synchronous interruption boundary remains documented.

Qualification

• Prior exact query candidate CI 38662841466 passes all ten jobs, including actual integration on exact qualified Server 2.8.0 source.
• Three real normally pulled Server 2.8.0 originals pass timely typed input/output, expiry during payload loading, and expiry during async handling, with one original query/deadline and no late completion submission. Prior Server 2.6.3 default-1.20 / explicit-1.19 compatibility is separate.
• This corrected version/source tree requires its own normal CI, publication and registry-installed acceptance. No tag or PyPI 2.5.15 claim yet.

[rmcdaniel]

Reviewed the corrected stable tree f493e6f / 4733ccc0 against the immutable published 2.5.14 baseline and prior qualified query candidate. Published backfill documentation is preserved, pending Nexus/main behavior is excluded, and no existing tag is reused. Exact corrected-tree CI 38665088931 passes every job, including pinned Server 2.8.0 integration and target-branch qualification; both boundary checks pass. Prior actual timely/loading-expiry/async-handler-expiry originals remain separate. Ready for compatible 2.5.15 publication and fresh registry-installed acceptance.

[rmcdaniel]

Exact corrected candidate CI 38665088931 passes all ten jobs and both boundary checks. PR153 is merged at 35aad4a, with tree 4733ccc04ddc9e0720c9c15ef9962216a765c2e0 byte-identical to the reviewed candidate. The existing 2.5.14 tag and PyPI package remain untouched. After confirming tag/index 2.5.15 was absent, immutable tag 2.5.15 now points to that merge; publication 38669469407 is queued. Registry-installed qualification and public portal follow-through remain pending, so this is not an installed delivery claim.