Add shared SQLite open macro with WASI crash recovery and in-memory temp storage

Card: SAU-249

sdk/src/lib.rs

@@ -392,6 +392,7 @@ mod error;
 mod helpers;
 mod imports;
 mod lines;
+mod sqlite;
 mod transport;
 pub use discovery::*;
 pub use endpoints::*;

sdk/src/sqlite.rs

@@ -0,0 +1,43 @@
+//! Shared SQLite open policy, expanded against the plugin's own rusqlite version.
+
+/// Open SQLite under an already-held Sausage host lock. The caller must depend
+/// on `rusqlite` (bundled) and hold the SAME host lock for EVERY connection's
+/// entire lifetime, including reads and old/new plugin versions. This macro does
+/// not acquire the lock. Do not use it for the host journal or databases accessed
+/// outside Sausage. Native builds retain OS locks; WASI selects `unix-none`, so
+/// crash-leftover dotfile lock directories cannot block recovery.
+///
+/// Temporary tables/sorts stay in memory before any schema access. Writable opens
+/// use DELETE journals; SQLite rolls back hot journals itself. Never delete a
+/// leftover journal. Read-only opens cannot recover a hot journal: recover with
+/// a writable open first.
+///
+/// The flags form preserves the caller's open flags. A macro avoids coupling the
+/// SDK to a particular rusqlite/libsqlite3-sys version (the host and plugins use
+/// different versions, which cannot coexist as dependencies due to `links`).
+///
+/// ```ignore
+/// let _guard = sausage_plugin::lock("/state/example/db.lock").await?;
+/// let c = sausage_plugin::sqlite_open!("/state/example/db.sqlite")?;
+/// // Query here; c must drop before _guard.
+/// ```
+#[macro_export]
+macro_rules! sqlite_open {
+    ($path:expr) => {
+        $crate::sqlite_open!($path, ::rusqlite::OpenFlags::default())
+    };
+    ($path:expr, $flags:expr) => {{
+        (|| -> ::rusqlite::Result<::rusqlite::Connection> {
+            let flags = $flags;
+            #[cfg(target_os = "wasi")]
+            let c = ::rusqlite::Connection::open_with_flags_and_vfs($path, flags, "unix-none")?;
+            #[cfg(not(target_os = "wasi"))]
+            let c = ::rusqlite::Connection::open_with_flags($path, flags)?;
+            c.pragma_update(None, "temp_store", "MEMORY")?;
+            if !flags.contains(::rusqlite::OpenFlags::SQLITE_OPEN_READ_ONLY) {
+                c.pragma_update(None, "journal_mode", "DELETE")?;
+            }
+            Ok(c)
+        })()
+    }};
+}