fix(23621): RedisClient Invalid URL (#23714)

### What does this PR do?

Fixes #23621.

Note that the quality of this code is quite low, but since Redis is
getting a rewrite, this is a stop-gap. The tests are what really matters
here.

This whole PR is claude.

### How did you verify your code works?

CI.

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

docs/api/redis.md

@@ -42,6 +42,7 @@ await client.incr("counter");
 By default, the client reads connection information from the following environment variables (in order of precedence):
 
 - `REDIS_URL`
+- `VALKEY_URL`
 - If not set, defaults to `"redis://localhost:6379"`
 
 ### Connection Lifecycle