fix(acp)!: preserve JSON-RPC frames across transport adapters

md/SUMMARY.md

@@ -25,6 +25,7 @@
 
 # Reference
 
+- [Migrating to v2.0](./migration_v2.0.md)
 - [Migrating to v0.11](./migration_v0.11.x.md)
 - [P/ACP Specification](./proxying-acp.md)
 

md/migration_v2.0.md

@@ -0,0 +1,26 @@
+# Migrating from `agent-client-protocol` 1.x to 2.0
+
+Version 2.0 changes the low-level in-process transport boundary so JSON-RPC frames remain intact
+across components and adapters.
+
+## Raw channels carry frames
+
+`Channel` is now the single batch-aware in-process transport boundary. Its `rx` and `tx` carry
+`TransportFrame`, not `Result<RawJsonRpcMessage, Error>`:
+
+```rust
+use agent_client_protocol::{Channel, RawJsonRpcMessage, TransportFrame};
+
+# fn send(channel: &Channel, message: RawJsonRpcMessage) {
+channel.tx.unbounded_send(TransportFrame::Single(message)).unwrap();
+# }
+```
+
+`TransportFrame` distinguishes a valid single message, a non-empty `TransportBatch`, and an
+explicit malformed wire value. Transport I/O failures are returned by the future from
+`ConnectTo::into_channel_and_future`; they are never channel items. Components should preserve a
+received frame intact when relaying it so batch response grouping remains correct.
+
+The separate, hidden `FramedChannel` and `into_framed_channel_and_future` compatibility path no
+longer exist. Implement only `ConnectTo::connect_to`, optionally overriding
+`into_channel_and_future` for a direct channel adapter.