feat(lib): AtomicNode runtime boundary (slice 1)

CHANGELOG.md

@@ -20,6 +20,15 @@ See [STATUS.md](server/STATUS.md) to learn more about which features will remain
   a store seeded by an older one. Existing values, including user edits to
   default resources, are never overwritten. `--repopulate-defaults` remains as
   a forced re-run with the same add-only semantics.
+- `atomic_lib`: `atomic_lib::runtime::AtomicNode` — a named node surface over
+  `Db` (`open`, `get`, `query`, `apply_commit(json, IngestPolicy)`, `mutate`,
+  `subscribe`, `sync_with_peer`). Thin delegation, no behaviour change; the
+  WASM `ClientDb` is the first adapter on it. `IngestPolicy::{Hub, Peer,
+  Replica, LocalCache}` names the four commit-validation profiles.
+  `sync::engine::ingest_commit` returns the `CommitResponse` that
+  `ingest_commit_json` serializes; `sync::ws_apply::apply_commit_json` now
+  returns the `CommitResponse` instead of `()`. See
+  `planning/runtime-boundary-decision.md`.
 
 ## [v0.41.0-beta.2] - 2026-08-01
 

TESTING_COVERAGE.md

@@ -121,6 +121,7 @@ Both matter because `iroh_transport` holds the router and node identity in
 | **`POST /iroh-sync` request shape, both sides** | `testdata/pairing-request.json` + `pairing.test.ts` + `iroh_pairing.rs` | shared fixture binds them |
 | Dart pairing-code parser, peer-sync result formatting | `flutter/test/atomic/` | pure parsers |
 | Rotation does not treat a metrics-change pop as "back to gallery" | `flutter/test/canvas/rotation_pop_test.dart` | |
+| `AtomicNode`: `mutate` on one node, `apply_commit(IngestPolicy::Peer)` on another, query + `DbEvent` reflect it | `lib/src/runtime/node.rs` | in-process, no transport; `LocalCache` skips signature check, `Peer` does not |
 
 ### Flow — the thin layer
 

lib/src/lib.rs

@@ -95,6 +95,9 @@ pub mod plugins;
 
 pub mod populate;
 pub mod resources;
+/// The node runtime boundary (`AtomicNode`). Wraps `Db`, so it needs `db`.
+#[cfg(feature = "db")]
+pub mod runtime;
 pub mod schema;
 pub mod serialize;
 pub mod store;

lib/src/runtime/mod.rs

@@ -0,0 +1,11 @@
+//! The node runtime boundary: [`AtomicNode`] is the one surface adapters
+//! (HTTP, WebSocket, Iroh, WASM, FFI, Flutter) bind to instead of wrapping
+//! [`crate::Db`] themselves.
+//!
+//! Slice 1 (`planning/atomic-lib-runtime.md`, `planning/runtime-boundary-decision.md`)
+//! is a thin wrapper: every method delegates to code that already existed, so
+//! there is no behaviour change — only a named place for it.
+
+mod node;
+
+pub use node::{AtomicNode, IngestPolicy, NodeConfig, NodeStorage, ResourceEdit};