Consolidate logic for protobuf message handling between ssh and web socket clients (#17185)

This is a refactor to prepare for adding LSP support in SSH remote
projects.

Release Notes:

- N/A

---------

Co-authored-by: Mikayla <mikayla@zed.dev>
Co-authored-by: Conrad <conrad@zed.dev>

crates/assistant/src/assistant.rs

@@ -209,7 +209,7 @@ pub fn init(
     })
     .detach();
 
-    context_store::init(&client);
+    context_store::init(&client.clone().into());
     prompt_library::init(cx);
     init_language_model_settings(cx);
     assistant_slash_command::init(cx);

crates/assistant/src/context_store.rs

@@ -2,6 +2,7 @@ use crate::{
     prompts::PromptBuilder, Context, ContextEvent, ContextId, ContextOperation, ContextVersion,
     SavedContext, SavedContextMetadata,
 };
+use ::proto::AnyProtoClient;
 use anyhow::{anyhow, Context as _, Result};
 use client::{proto, telemetry::Telemetry, Client, TypedEnvelope};
 use clock::ReplicaId;
@@ -25,7 +26,7 @@ use std::{
 };
 use util::{ResultExt, TryFutureExt};
 
-pub fn init(client: &Arc<Client>) {
+pub fn init(client: &AnyProtoClient) {
     client.add_model_message_handler(ContextStore::handle_advertise_contexts);
     client.add_model_request_handler(ContextStore::handle_open_context);
     client.add_model_request_handler(ContextStore::handle_create_context);