Use VWS Python Mock 2026.8.4

[adamtheturtle]

• Bump VWS Python Mock to 2026.8.4 and align package metadata, documentation, and CI with its Python 3.14 minimum.
• Exercise the mock's new quota and project-state responses through both synchronous and asynchronous clients, removing obsolete coverage exclusions.
• Add the Towncrier fragment for Add test which hits RequestQuotaReached #822.
• Validation: 319 tests pass with 100% coverage, and pre-commit plus all configured type checkers pass.

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Note

Medium Risk
Requiring Python 3.14 is a breaking change for anyone still on 3.13; runtime client logic is largely unchanged aside from better test coverage of existing error mappings.

Overview
Raises the minimum Python version to 3.14 (drops 3.13) across pyproject.toml, README, and CI/lint/docs workflows so they only run on 3.14.

Bumps vws-python-mock to 2026.8.4 and adds sync/async tests that drive quota and project-state errors (RequestQuotaReached, TargetQuotaReached, ProjectSuspended, ProjectHasNoAPIAccess) through the mock. Removes # pragma: no cover on those exception classes now that the mock covers them.

Includes minor Ruff typing-import cleanup (TC001/TC003, TYPE_CHECKING for Awaitable in transports) and a Towncrier fragment for #822.

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