chore(call): prune connect, TLS helpers, CallCredentials, and dead paths (Phase 5)

- Remove RemoteIdentity, CallCredentials, ClientError, connect() from call_client.rs
- Remove all TLS helpers (build_quinn_client_config, build_client_auth,
  select_server_verifier, FingerprintPinVerifier, RawKeyClientCertResolver,
  NoClientCertResolver, Ed25519SigningKey, cert/key loaders)
- Remove credentials_auth_token dead path from from_call.rs
  (OpSummary field, build_bundles, make_forwarding_handler,
  make_streaming_forwarding_handler, build_forwarded_payload)
- Remove 2 dead-path tests (build_forwarded_payload_sets_auth_token,
  streaming_forwarding_handler_sets_auth_token)
- Update mod.rs re-exports to only CallClient
- Remove quinn feature and TLS deps from Cargo.toml
- Delete tests/two_node_call.rs (used connect() + CallCredentials)
- alknet-call is now a pure protocol crate

crates/alknet-call/Cargo.toml

@@ -3,15 +3,14 @@ name = "alknet-call"
 version.workspace = true
 edition.workspace = true
 license.workspace = true
-description = "Structured RPC over QUIC on ALPN `alknet/call`: operations, streaming subscriptions, service discovery"
+description = "Structured RPC over ALPN `alknet/call`: operations, streaming subscriptions, service discovery"
 repository.workspace = true
 
 [lib]
 name = "alknet_call"
 
 [features]
-default = ["quinn"]
-quinn = ["dep:quinn", "dep:rustls", "dep:rustls-native-certs", "dep:rustls-pemfile", "alknet-core/quinn"]
+default = []
 
 [dependencies]
 alknet-core = { path = "../alknet-core" }
@@ -24,11 +23,3 @@ thiserror = "2"
 uuid = { version = "1", features = ["v4"] }
 futures = "0.3"
 parking_lot = "0.12"
-quinn = { version = "0.11", optional = true }
-rustls = { version = "0.23", optional = true, features = ["aws_lc_rs"] }
-rustls-native-certs = { version = "0.8", optional = true }
-rustls-pemfile = { version = "2", optional = true }
-
-[dev-dependencies]
-rcgen = "0.13"
-hex = "0.4"