feat: Add first-class Valkey support with GLIDE-backed store

[janisto]

Adds first-class Valkey support to @fastify/rate-limit through a new valkey option backed by a dedicated ValkeyStore that uses @valkey/valkey-glide scripting APIs. It keeps the existing Redis path unchanged, adds runtime validation for mutually exclusive storage options, and updates the public type surface with a structural Valkey client interface.

It also adds documentation and examples for both direct GLIDE clients and @fastify/valkey-glide, plus expanded test coverage for Valkey behavior including ban, skipOnError, throw-on-error, continueExceeding, exponentialBackoff, route-scoped limits, and createRateLimit(). Verification now runs Redis and Valkey integration backends on separate ports so both suites can execute without cross-test interference.

Close #436

See fastify/fastify-valkey-glide#33

Checklist

• run npm run test && npm run benchmark --if-present
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[Copilot]

Pull request overview

Adds first-class Valkey support to @fastify/rate-limit by introducing a new valkey configuration option backed by a GLIDE-scripted ValkeyStore, plus documentation/examples and new test coverage.

Changes:

• Add ValkeyStore implementation using @valkey/valkey-glide scripting APIs and wire it into plugin initialization via settings.valkey.
• Add runtime validation to enforce mutual exclusivity between store, redis, and valkey.
• Extend TypeScript types, docs, examples, and add unit + integration tests for Valkey behavior.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
index.js	Adds valkey store selection and validates mutually exclusive store options.
store/ValkeyStore.js	New GLIDE-backed store implementation using cached script invocation.
types/index.d.ts	Adds FastifyRateLimitValkeyClient, adjusts option types (redis to unknown, valkey added).
types/index.test-d.ts	Adds type-level coverage for valkey option and client interface.
test/valkey-store.test.js	Unit tests for ValkeyStore key prefixing, child behavior, caching, and error forwarding.
test/valkey-rate-limit.test.js	Plugin-level tests for valkey option and new mutual exclusivity validation.
test/valkey-real-rate-limit.test.js	Real integration tests against a running Valkey backend (GLIDE client).
example/example-valkey-direct.mjs	Example using a directly managed GLIDE client.
example/example-fastify-valkey-glide.mjs	Example using @fastify/valkey-glide to supply the resolved client.
README.md	Documents Valkey usage, installation guidance, and examples.
package.json	Adds optional peer + dev dependency on @valkey/valkey-glide and a local valkey docker script.

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