ci: qualify CPython 3.14 and bound interpreter support

[doublewhy]

Problem

The package metadata currently admits every future CPython release with requires-python >=3.11, while CI verifies only Python 3.12. PR #1089 adds a matrix but does not bound metadata, prove a clean wheel install, or add the requested free-threaded preview posture.

Scope

This issue is about OpenRAE itself, not experiment repositories.

Requirement: GOV-901.

Acceptance

• Set the supported standard interpreter range to CPython 3.11 through 3.14 with requires-python >=3.11,<3.15 and matching Trove classifiers.
• Replace event-loop-dependent MCP tests with asyncio.run as in test(mcp): drive MCP tool calls through asyncio.run #1087.
• Run a blocking, exact-interpreter compatibility matrix for 3.11, 3.12, 3.13, and 3.14. The job must assert the interpreter actually selected, install from the frozen lock, run the hermetic suite, build the wheel, install it into a clean environment, and smoke the public CLI/import surface.
• Add a nonblocking 3.14t preview on scheduled/manual runs. Assert that the selected build is free-threaded; do not advertise 3.14t as a production support guarantee.
• Do not add or test Python 3.15 before its final release. Qualification after final requires a separate issue and wheel/dependency review.
• Document the difference between Requires-Python, tested standard interpreters, and the preview lane.
• Keep canonical verification, policy, and release gates green.

Related

• test(mcp): drive MCP tool calls through asyncio.run #1087 supplies the correct MCP test-loop change.
• ci: test every interpreter the project claims to support #1089 is useful input but must be superseded by the bounded metadata and clean-install design above.