Split into acp-mux core + rooms collaboration layer

CHANGELOG.md

@@ -2,27 +2,70 @@
 
 ## Unreleased
 
+### Breaking
+
+- **Collaboration layer renamed `amux` → `rooms`.** The crate, library, and
+  binary are now `rooms`, and the wire namespace changed accordingly:
+  - `amux/*` notification/control methods → `rooms/*` (e.g. `amux/turn_started`
+    → `rooms/turn_started`, `amux/queue_prompt` → `rooms/queue_prompt`).
+  - `_meta.amux` → `_meta.rooms` (on `session/attach` results and propagated
+    request metadata); the `session/list` decoration key moved likewise.
+  - The `amuxTurnId` field is now `roomsTurnId`.
+  Clients written against the previous `amux/*` releases must update method
+  names and `_meta` keys. The lower-level core crate/binary stays `acp-mux`.
+
 ### Added
 
+- **Two-crate workspace: core mux vs Rooms layer.** The repo is now a Cargo
+  workspace with a hard, compiler-enforced boundary:
+  - `acp-mux` (lib `acp_mux`, binary `acp-mux`) — the standalone generic 1→N
+    ACP multiplexer. Id translation, response routing, first-writer-wins
+    agent-request fan-in, `initialize`/`session/new` caching, `fs/*`/`terminal/*`
+    safety, plain replay/late-join, and an RFD-#533-baseline
+    `session/attach`/`session/detach`. It contains zero `rooms/*` knowledge and
+    does not depend on the `rooms` crate. The standalone binary attaches on
+    `?mux=<id>`.
+  - `rooms` (lib `rooms`, binary `rooms`) — the Rooms collaboration protocol,
+    implemented as a `MuxExtension` plugged into the core mux actor. Owns turns,
+    queue/steer/cancel, presence, segments, `_meta.rooms` attach
+    enrichment, and all `rooms/*` frames. Depends on `acp-mux`. The `rooms`
+    binary attaches on `?room=<id>`.
+  - The boundary is realized through a `MuxExtension` trait + `MuxCtx`
+    capability surface in core (core ships a no-op extension; `rooms` provides
+    the real one). There is now a single multiplexer implementation.
+- **Standalone `acp-mux` binary.** A pure one-agent-to-many-clients mux with no
+  collaboration layer, for clients that only need raw ACP mirroring.
 - **Optional persistent replay store.** `--replay-store <DIR>` persists
-  broadcast-tier room history as append-only JSONL and rehydrates replay
-  frames/segment bookends on restart. The upstream agent still owns actual
-  conversation state.
+  broadcast-tier room history as append-only JSONL and rehydrates the broadcast
+  replay log on restart so late joiners can recover the transcript via
+  `historyPolicy: full_lineage`. Segment lineage and current-segment (`full`)
+  scoping are not reconstructed across restart yet — see the "cross-restart
+  segment fidelity" limitation in `docs/design/rooms.md`. The upstream agent
+  still owns actual conversation state.
 - **Client contract fixtures.** `docs/examples/client-contract/` contains
   copyable request/response/notification JSON fixtures for `session/attach`,
   turn lifecycle, queue lifecycle, agent-request lifecycle, replay markers,
   and segment lineage.
 
 ### Changed
 
+- **Library reorganized into two crates.** Core multiplexing moved from
+  `src/room/state.rs` (`RoomInner`) into `crates/acp-mux/src/mux/` (`MuxCore` +
+  actor) with no `rooms/*` concerns; the collaboration behavior moved into
+  `crates/rooms/src/extension/` (`RoomsExtension: MuxExtension`). The `rooms`
+  crate's `RoomRegistry`/`server` are now thin wrappers over the core
+  `MuxRegistry::with_extension(...)`. Aside from the `amux/*` → `rooms/*`
+  namespace rename above, the `rooms` binary's behavior is otherwise unchanged;
+  the integration suite and `docs/examples/client-contract/` fixtures were
+  updated to the new namespace and still pass.
 - **Provider-neutral core contract.** The mainline mux is now documented and
   implemented as a generic ACP multiplexer / agent mirror rather than a
   provider-specific adapter. Provider metadata is passed through opaquely;
   mux-owned lifecycle state is driven only by JSON-RPC envelopes, ACP method
   names, `session/load`, and observable ACP `params.sessionId` changes.
 - **Docs reframed around rooms, mirrors, and generic ACP clients.** README,
   roadmap, and design docs now describe `acp-mux` as a reusable ACP room
-  server with provider-neutral safety defaults and an explicit `amux/*`
+  server with provider-neutral safety defaults and an explicit `rooms/*`
   side channel.
 
 ### Removed

Cargo.toml

@@ -1,31 +1,3 @@
-[package]
-name = "acp-mux"
-version = "0.1.3"
-edition = "2024"
-
-# The crate (and GitHub repo) is "acp-mux" but the installed binary is
-# the shorter "amux". `src/bin/mock_acp.rs` is still auto-detected.
-# The library exists so integration tests under `tests/` can use the
-# server/registry/protocol modules without spawning the binary.
-[lib]
-name = "amux"
-path = "src/lib.rs"
-
-[[bin]]
-name = "amux"
-path = "src/main.rs"
-
-[dependencies]
-anyhow = "1.0.102"
-axum = { version = "0.8.9", features = ["ws", "macros"] }
-bytes = "1.11.1"
-clap = { version = "4.6.1", features = ["derive"] }
-futures = "0.3.32"
-serde = { version = "1.0.228", features = ["derive"] }
-serde_json = "1.0.149"
-thiserror = "2.0.18"
-tokio = { version = "1.52.3", features = ["full"] }
-tokio-tungstenite = "0.29.0"
-tracing = "0.1.44"
-tracing-subscriber = { version = "0.3.23", features = ["env-filter", "fmt"] }
-url = "2.5.8"
+[workspace]
+members = ["crates/acp-mux", "crates/rooms"]
+resolver = "3"