Initial commit: ClawSync v0.1.0

8-crate pure-Rust workspace for revision-aware HDF5 sync.

## Crates
- clawhdf5-onion: ClawOnion VFD — page-level versioned HDF5 storage,
  binary format, writer/reader, branch DAG, GC, snapshots, provenance
- clawsync-core: BLAKE3, xxHash3, FastCDC (+ SIMD NEON), zstd/lz4
- clawsync-onion: IBLT sketch, Merkle tree differ, packet differ/merger,
  ClawSyncManifest, SyncSelector
- clawsync-hdf5: dataset-level manifest, differ, patcher, wire payload
  reconstruction (apply_received_payloads)
- clawsync-transport: TCP, QUIC (quinn 0.11/TLS 1.3), SyncPeer abstraction,
  length-prefixed rkyv wire protocol (21 SyncMessage variants)
- clawsync-agent: OnionMemory, SyncScheduler, TcpSyncBackend,
  PeerCapabilities negotiation
- clawsync-fs: CDC-based delta sync for any file type; FsSyncClient/Server,
  W=16 pipelining, atomic writes
- clawsync-cli: push/pull/serve/hdf5-sync/serve-hdf5/sync/serve-fs +
  all local management commands; --quic on all network commands

## Key features
- IBLT pre-flight: O(revision count) vs rsync's O(file size)
- W=16 sliding-window push: 13–15x speedup over stop-and-wait at WAN RTT
- Dataset-granular HDF5 sync: only modified datasets transferred
- CDC delta for any file type: insertion-stable chunk boundaries
- Full revision DAG: branch, merge, rollback, export, snapshot, GC
- QUIC transport: TLS 1.3, per-message streams via quinn 0.11

## Tests
~573 passing (default features); ~589 with --features simd-cdc

## Performance (Apple Silicon)
- Reconstruct rev=100: 68 µs (target ≤ 1 ms)
- BLAKE3 Rayon 1 MB: 10.3 GiB/s (target ≥ 5 GB/s)
- GC 500 revisions: 20.6 µs (target ≤ 2 s)
- W=16 vs W=1 at 5 ms RTT: 14.8x speedup
- No-op pre-flight at 16 MB: 4 ms vs rsync 35 ms (7.8x)

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

crates/clawhdf5-onion/README.md

@@ -0,0 +1,76 @@
+# clawhdf5-onion
+
+Pure-Rust ClawOnion VFD — revision-layered HDF5 versioning with DAG branching.
+
+## Overview
+
+`clawhdf5-onion` implements the **ClawOnion Virtual File Driver**: a zero-C-dependency
+versioning layer for HDF5 files that stores write sessions as page-level diffs in a
+`.onion` sidecar file. Any historical revision can be reconstructed without modifying
+the original `.h5` file.
+
+The metaphor: the original file state is the core; each write session adds a new skin
+of page changes on top.
+
+## Features
+
+- **Revision history** — every write session becomes an immutable revision; open any past state read-only
+- **DAG branching** — fork, write, and merge branches with three merge strategies (last-write-wins, dataset-level resolver, three-way)
+- **BLAKE3 provenance** — per-revision content hashing for tamper detection
+- **Per-page compression** — zstd or lz4 with configurable codec per session
+- **Snapshot checkpoints** — bounds reconstruction cost at deep revision history
+- **GC policies** — keep-last-N, keep-tagged, keep-since to reclaim space
+- **No C dependencies** — pure Rust
+
+## Usage
+
+```rust
+use clawhdf5_onion::writer::OnionFile;
+
+// Create a new versioned file pair (.h5 + .h5.onion)
+let mut onion = OnionFile::create("data.h5", 4096)?;
+
+// Write a session
+let mut session = onion.begin_session(None)?;
+session.record_page(0, &page_bytes);
+onion.commit_session(session, Some("initial import"))?;
+
+// Open a historical revision
+let bytes_at_rev0 = onion.open_revision(0)?;
+```
+
+The `VersionedFile` wrapper integrates with `clawhdf5::File` for high-level access:
+
+```rust
+use clawhdf5_onion::versioned_file::VersionedFile;
+
+let vf = VersionedFile::open("data.h5")?;
+// ... use the clawhdf5 File API on the HEAD revision
+let historical = clawhdf5_onion::open_at_revision("data.h5", 3)?;
+```
+
+## Format
+
+The `.onion` sidecar uses a fixed binary layout (ClawOnion v1):
+
+| Section | Size |
+|---|---|
+| `OnionHeader` | 128 bytes |
+| `RevisionIndex` | 112 bytes × N revisions |
+| `BranchManifest` | 40 bytes × B branches |
+| `PageTable` entries | 32 bytes × P pages |
+| `PageData` | compressed page bytes |
+| `AnnotationHeap` | length-prefixed UTF-8 strings |
+
+## Feature Flags
+
+| Feature | Default | Description |
+|---|---|---|
+| `provenance` | on | BLAKE3 per-revision page hashing |
+| `compress` | on | per-page zstd/lz4 compression |
+| `parallel` | off | Rayon parallel page hashing |
+| `async` | off | Tokio async flush |
+
+## License
+
+MIT — see repository root.