fix(crate): declare getrandom std feature and gate wasm-incompatible module

Publishing pagedb standalone (outside the workspace) exposed two gaps
masked by feature unification: getrandom needs `std` for
PagedbError::Randomness to satisfy getrandom::Error: std::error::Error,
and manifest_validation imports a wasm-gated snapshot type, so it must
be gated the same way to keep the wasm32 build compiling.

Author: farhan-syah

Cargo.toml

@@ -32,7 +32,12 @@ bytes = "1"
 tracing = "0.1"
 parking_lot = "0.12"
 rayon = "1"
-getrandom = { version = "0.2", features = ["js"] }
+# `std` is required (not just `js`): `PagedbError::Randomness(#[from]
+# getrandom::Error)` relies on `getrandom::Error: std::error::Error`, which
+# getrandom only provides under `std`. In the workspace a sibling crate enabled
+# `std` via feature unification, masking the gap — published standalone, pagedb
+# must declare the feature it actually uses.
+getrandom = { version = "0.2", features = ["js", "std"] }
 
 # tokio's `rt-multi-thread` and `fs` features are not supported on
 # `wasm32-unknown-unknown`. Split per target so OPFS builds compile.

src/txn/db/mod.rs

@@ -5,6 +5,11 @@ mod apply_journal;
 mod catalog;
 mod core;
 mod gc;
+// Serves the native-only incremental-snapshot apply path: its sole caller is
+// `snapshot` (wasm-gated below) and it imports `SnapshotManifest` from the
+// wasm-gated `crate::snapshot::export`. Gate it the same way so the wasm build
+// does not pull an import that is configured out.
+#[cfg(not(target_arch = "wasm32"))]
 mod manifest_validation;
 mod misc;
 mod open;