Core tests open their store through local::memory_conn

Seven test modules each built a migrated in-memory store by hand: open, migrate,
and (in sharing) wrap it in a Db. local::memory_conn() is that, and
open_in_memory uses it too. Each module's db() is now one line, and the schema,
Connection and Mutex imports it needed are gone.

DRY pass #2, batch 2, F9 (#5372).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

core/src/local/mod.rs

@@ -77,9 +77,15 @@ pub fn open(path: &Path) -> rusqlite::Result<Db> {
 /// crate was doing before the core was extracted. The Android bindings will want the
 /// same thing.
 pub fn open_in_memory() -> rusqlite::Result<Db> {
+    Ok(Db(Mutex::new(memory_conn()?)))
+}
+
+/// A migrated, in-memory connection: [`open_in_memory`]'s, and every core test's
+/// store.
+pub(crate) fn memory_conn() -> rusqlite::Result<Connection> {
     let conn = Connection::open_in_memory()?;
     schema::migrate(&conn)?;
-    Ok(Db(Mutex::new(conn)))
+    Ok(conn)
 }
 
 /// A one-line count summary of the store, for the startup log.

core/src/local/portable.rs

@@ -593,11 +593,9 @@ fn dirname(path: &str) -> &str {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::local::schema;
 
     fn store() -> (Connection, BlobStore, std::path::PathBuf) {
-        let conn = Connection::open_in_memory().unwrap();
-        schema::migrate(&conn).unwrap();
+        let conn = crate::local::memory_conn().unwrap();
         let dir = std::env::temp_dir().join(format!("inkwell-portable-{}", uuid::Uuid::new_v4()));
         let blobs = BlobStore::new(dir.clone()).unwrap();
         (conn, blobs, dir)

core/src/local/retention.rs

@@ -80,12 +80,9 @@ pub fn sweep_if_unlinked(conn: &Connection) -> rusqlite::Result<Option<usize>> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::local::schema;
 
     fn db() -> Connection {
-        let conn = Connection::open_in_memory().expect("in-memory db");
-        schema::migrate(&conn).expect("migrate");
-        conn
+        crate::local::memory_conn().expect("in-memory db")
     }
 
     /// A trashed note of a given age, stamped in the format the CLIENT writes

core/src/local/store.rs

@@ -1143,12 +1143,9 @@ mod tests {
     //! against a real schema catches, which is what every test here runs.
 
     use super::*;
-    use crate::local::schema;
 
     fn db() -> Connection {
-        let conn = Connection::open_in_memory().expect("in-memory db");
-        schema::migrate(&conn).expect("migrate");
-        conn
+        crate::local::memory_conn().expect("in-memory db")
     }
 
     fn note(conn: &Connection, body: &str) -> Note {