action(services): support isolated Redis on Windows runners

Gap

The first-class services: input starts and health-checks Redis on Linux and macOS runners. Windows is rejected explicitly because upstream Redis does not publish a supported native Windows server and Pantry must not silently substitute an unrelated implementation.

Required work

• Choose and document a Redis-compatible Windows runtime with an explicit compatibility policy (for example, a maintained Valkey/Redis-compatible distribution or a managed container path).
• Install it through Pantry with immutable version and integrity metadata.
• Start it loopback-only with ephemeral data, export the same REDIS_URL and REDIS_SERVICE_VERSION contract, and shut it down in the action post step.
• Add a windows-2025 live round-trip workflow job and retain the resolved implementation/version in the step summary.

Acceptance criteria

• services: redis@X.Y.Z has defined semantics on Windows or fails at version resolution with a documented incompatibility.
• Start, health check, set/get, and cleanup are tested on windows-2025.
• Linux/macOS behavior and exact version checks remain unchanged.