add bus compression settings to PSRPCConfig

[paulwe]

Surfaces the opt-in gzip compression added in psrpc#130 (released as v0.7.6) as configuration, so services that already carry a PSRPCConfig can enable it from their psrpc: yaml block.

psrpc:
  compression:
    quality: 6
    threshold: 1024
    max_decompressed_size: 0

Shape

CompressionConfig is its own type rather than an alias for psrpc.CompressionOpts. The fields match one for one, but CompressionOpts carries no yaml tags, so keys would marshal as maxdecompressedsize, and livekit-server's configtest.CheckYAMLTags recurses into nested config structs and requires omitempty on every exported non-bool field.

BusOptions() is the single conversion into psrpc bus options, alongside the existing (*ClientParams).Options(). Value receiver, because getPSRPCConfig(conf) returns a non-addressable PSRPCConfig. It returns the option unconditionally: WithBusCompression with Quality <= 0 leaves the compressor nil, and MaxDecompressedSize still has to reach the read side when publishing is off.

It stops short of a rpc.NewMessageBus helper — livekit-server picks redis-vs-local, cloud uses NATS, and each is already a wire provider.

Default is off

Quality defaults to zero. A peer on a psrpc older than v0.7.6 cannot decode a compressed payload, and psrpc's subscription read loop drops undecodable messages, so a deployment has to be fully upgraded before publishers raise it. Threshold is seeded from psrpc.DefaultCompressionThreshold so the effective value is visible in a dumped config.

Notes

• Adding the field is source-compatible: the only PSRPCConfig{...} literal is DefaultPSRPCConfig here, and it is keyed.
• The google.golang.org/grpc patch bump comes from psrpc v0.7.6 via MVS.
• The livekit-server side is wire psrpc bus compression into the message bus constructor livekit#4844.

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Latest commit: 58b6510

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
github.com/livekit/protocol	Patch
@livekit/protocol	Patch

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