feat(agent): add ssh_scheduler + update README with diff, SshSyncBackend, test count

- ssh_scheduler() convenience constructor mirrors tcp_scheduler for SSH backend
- Re-exported from clawsync_agent crate root
- README: diff command section, SshSyncBackend library usage table + example,
  updated crate interdependency description, test count 617→644

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

README.md

@@ -163,7 +163,7 @@ crates/
   clawsync-onion/     Packet differ/merger, IBLT sketch, Merkle tree, ClawSyncManifest
   clawsync-hdf5/      Dataset-level manifest, differ, patcher (HDF5-aware sync)
   clawsync-transport/ TCP, QUIC (quinn 0.11/TLS 1.3), length-prefixed wire protocol
-  clawsync-agent/     OnionMemory, SyncScheduler, TcpSyncBackend, capability negotiation
+  clawsync-agent/     OnionMemory, SyncScheduler, TcpSyncBackend/QuicSyncBackend/SshSyncBackend
   clawsync-fs/        CDC-based delta sync for any file type (FsSyncClient, FsSyncServer)
   clawsync-cli/       clawsync binary — all commands wired here
 ```
@@ -193,7 +193,7 @@ The workspace `.cargo/config.toml` sets `target-cpu=native` for SIMD throughput
 ### Run tests
 
 ```bash
-cargo test --workspace                          # ~573 tests
+cargo test --workspace                          # ~644 tests
 cargo test --workspace --features simd-cdc     # +16 SIMD CDC tests
 cargo bench -p clawhdf5-onion                  # Criterion benchmarks
 ```
@@ -642,6 +642,33 @@ clawsync branch merge model.h5 experiment --into main --strategy latest-wins
 
 ---
 
+### diff
+
+Show page-level differences between two revisions of a local `.onion` sidecar. If `REV2` is omitted, compares `REV1` against the current HEAD.
+
+```bash
+clawsync diff <LOCAL.h5> <REV1> [REV2] [--porcelain]
+```
+
+```bash
+clawsync diff model.h5 5 8
+# Diff rev 5 → rev 8:
+#   ~  page 0  (changed, 4096 B)
+#   +  page 12 (added, 4096 B)
+#   -  page 7  (removed)
+# 1 page(s) changed, 1 added, 1 removed.
+
+# Machine-readable output
+clawsync diff model.h5 5 8 --porcelain
+# ~	0	4096
+# +	12	4096
+# -	7
+```
+
+Detection is based on `data_offset` equality in the append-only sidecar: two revisions referencing the same offset contain identical bytes, so a changed entry is unambiguous without decompressing any page data.
+
+---
+
 ## Transport: TCP, QUIC, and SSH
 
 All network commands support TCP (default), QUIC (`--quic`), and SSH (automatic when the remote address contains `@`).
@@ -774,7 +801,7 @@ cargo build --workspace --release
 ### Testing
 
 ```bash
-# All tests (~617 default, ~633 with SIMD CDC)
+# All tests (~644 default, ~660 with SIMD CDC)
 cargo test --workspace
 cargo test --workspace --features simd-cdc
 
@@ -809,6 +836,50 @@ clawsync-cli
         └── clawsync-core (BLAKE3, xxHash3, FastCDC, zstd)
 ```
 
+### Using `clawsync-agent` as a library
+
+The `clawsync-agent` crate exposes a `SyncBackend` trait with three implementations:
+
+| Backend | When to use |
+|---------|-------------|
+| `TcpSyncBackend` | Pre-running `clawsync serve` on LAN |
+| `QuicSyncBackend` | Encrypted WAN, pre-running `clawsync serve --quic` |
+| `SshSyncBackend` | No pre-running server; spawns `clawsync serve --stdio` on demand |
+
+```rust
+use clawsync_agent::{SshSyncBackend, SyncBackend, ssh_scheduler};
+use clawsync_agent::{TcpSyncBackend, tcp_scheduler};
+use clawsync_onion::selector::SyncSelector;
+
+// SSH — no daemon needed
+let scheduler = ssh_scheduler(
+    "[email protected]",
+    "/data/agent.claws",
+    local_h5_path,
+    "my-agent",
+    SyncSelector::All,
+);
+
+// TCP — pre-running serve required
+let scheduler = tcp_scheduler(
+    "127.0.0.1:9999",
+    local_h5_path,
+    "my-agent",
+    SyncSelector::All,
+)?;
+
+// Drive the scheduler manually
+let stats = scheduler.sync_once().await?;
+
+// Or hook into OnionMemory for autonomous post-flush sync
+use clawsync_agent::OnionMemory;
+let backend = SshSyncBackend::new("user@host", "/remote/agent.claws", "agent-1");
+let memory = OnionMemory::new(local_h5_path, backend);
+memory.record_and_flush(data).await?;
+```
+
+Override the SSH binary (e.g. for testing) by setting `CLAWSYNC_SSH_COMMAND` or calling `.with_ssh_command(path)` on the backend.
+
 ### Wire protocol stability
 
 `SyncMessage` variants are serialized with rkyv and assigned discriminants positionally. **Never insert or reorder variants** — always append. The current variant list:

crates/clawsync-agent/src/lib.rs

@@ -3,7 +3,7 @@
 //!
 //! ## Modules
 //!
-//! - [`backend`]: `SyncBackend` trait + `TcpSyncBackend` / `QuicSyncBackend` implementations
+//! - [`backend`]: `SyncBackend` trait + `TcpSyncBackend` / `QuicSyncBackend` / `SshSyncBackend`
 //! - [`onion_memory`]: `OnionMemory` — revision-aware wrapper around `HDF5Memory`
 //! - [`scheduler`]: `SyncScheduler` — autonomous push after each flush
 //! - [`negotiator`]: Peer capability negotiation
@@ -38,4 +38,4 @@ pub use backend::{
 pub use error::AgentSyncError;
 pub use negotiator::{SessionCapabilities, assert_compatible, negotiate};
 pub use onion_memory::{MemorySnapshot, OnionMemory};
-pub use scheduler::{SyncScheduler, tcp_scheduler};
+pub use scheduler::{SyncScheduler, ssh_scheduler, tcp_scheduler};

crates/clawsync-agent/src/scheduler.rs

@@ -103,6 +103,31 @@ pub fn tcp_scheduler(
     ))
 }
 
+/// Convenience constructor: create a [`SyncScheduler`] backed by
+/// [`SshSyncBackend`].
+///
+/// - `user_host` — SSH target, e.g. `"[email protected]"`
+/// - `remote_path` — absolute path on the remote, e.g. `"/data/agent.claws"`
+/// - `h5_path` — local HDF5 file to sync
+/// - `agent_id` — identifier sent in protocol messages
+/// - `selector` — which revisions to push
+///
+/// The `CLAWSYNC_SSH_COMMAND` environment variable overrides the SSH binary
+/// (defaults to `ssh`).
+pub fn ssh_scheduler(
+    user_host: &str,
+    remote_path: &str,
+    h5_path: PathBuf,
+    agent_id: &str,
+    selector: SyncSelector,
+) -> SyncScheduler<crate::backend::SshSyncBackend> {
+    SyncScheduler::new(
+        crate::backend::SshSyncBackend::new(user_host, remote_path, agent_id),
+        h5_path,
+        selector,
+    )
+}
+
 // ─────────────────────────────────────────────────────────────────────────────
 // Tests
 // ─────────────────────────────────────────────────────────────────────────────