DRY pass #3: core tests open their store and seed a label one way (#5373)

Five test modules wrote the same db() over memory_conn, and portable.rs
unwrapped it inline; local::test_db() is that. Four pull/push tests wrote the
same label INSERT; local::seed_label(conn, id, name, dirty) is it. Both are
cfg(test), beside memory_conn, as wire::sample_note is beside wire::Note.

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

core/src/local/mod.rs

@@ -88,6 +88,23 @@ pub(crate) fn memory_conn() -> rusqlite::Result<Connection> {
     Ok(conn)
 }
 
+/// A test's store: [`memory_conn`], which can't fail on a fresh in-memory database.
+#[cfg(test)]
+pub(crate) fn test_db() -> Connection {
+    memory_conn().expect("in-memory db")
+}
+
+/// A label this device holds, by id and name, for tests that need one in place.
+#[cfg(test)]
+pub(crate) fn seed_label(conn: &Connection, id: &str, name: &str, dirty: i64) {
+    conn.execute(
+        "INSERT INTO labels (id, name, color, created_at, updated_at, dirty)
+              VALUES (?1, ?2, 'default', '2026-01-01', '2026-01-01', ?3)",
+        rusqlite::params![id, name, dirty],
+    )
+    .expect("seed label");
+}
+
 /// A one-line count summary of the store, for the startup log.
 pub fn summary(db: &Db) -> String {
     let conn = match db.conn() {

core/src/local/portable.rs

@@ -595,7 +595,7 @@ mod tests {
     use super::*;
 
     fn store() -> (Connection, BlobStore, std::path::PathBuf) {
-        let conn = crate::local::memory_conn().unwrap();
+        let conn = crate::local::test_db();
         let blobs = crate::sync::blobs::scratch("portable");
         let dir = blobs.root().to_path_buf();
         (conn, blobs, dir)

core/src/local/retention.rs

@@ -81,9 +81,7 @@ pub fn sweep_if_unlinked(conn: &Connection) -> rusqlite::Result<Option<usize>> {
 mod tests {
     use super::*;
 
-    fn db() -> Connection {
-        crate::local::memory_conn().expect("in-memory db")
-    }
+    use crate::local::test_db as db;
 
     /// A trashed note of a given age, stamped in the format the CLIENT writes
     /// (`...Z`, millisecond precision — see `store::now`).

core/src/local/store.rs

@@ -1123,9 +1123,7 @@ mod tests {
 
     use super::*;
 
-    fn db() -> Connection {
-        crate::local::memory_conn().expect("in-memory db")
-    }
+    use crate::local::test_db as db;
 
     fn note(conn: &Connection, body: &str) -> Note {
         create_note(