android: the handoff — the pending rounds, the pipeline, and what is unverified

Everything written this session that has not been through the device: rounds 43
to 48 (each patch adversarially verified, 43's transient-notice expectation
fixed), a partial round 49, the pipeline scripts, the Android Auto design and
the icon comparison mock. Also the two harness changes that were never A/B'd —
adaptive waits, which may only shorten a declared wait and never lengthen it,
and a ship that runs the mock walk and the deploy at the same time. The A/B and
its 255-step baseline are in handoff/tools; main stays at what the phone has
actually walked.

handoff/rounds/ins-r51-library-ro.txt

@@ -0,0 +1,32 @@
+    /// Open an EXISTING database without writing a byte to it.
+    ///
+    /// [`Library::open`] cannot be used from a process that does not own the
+    /// library: it runs `PRAGMA journal_mode = WAL` and a batch of
+    /// `CREATE TABLE IF NOT EXISTS`, both writes, and on Android it may be
+    /// racing the real app. Android Auto browses and plays from a
+    /// service-started process with no Activity in it, and this is the door
+    /// it uses.
+    ///
+    /// A read-only open of a WAL database is legal from SQLite 3.22 (this
+    /// tree bundles 3.46) as long as the `-shm` and `-wal` files exist and
+    /// are readable, OR there is write permission on the DIRECTORY holding
+    /// the database. The second always holds for us — the reader is the
+    /// app's own uid and owns `…/Library/.soulstream/` — which is why this
+    /// works even though `journal_mode=WAL` is persistent and every
+    /// SoulStream database is in it.
+    ///
+    /// `NO_MUTEX` because the connection is behind this struct's own
+    /// `Mutex`; `URI` because the default flags carry it and dropping it
+    /// would quietly change how a path with a `?` in it is read.
+    pub fn open_read_only(db_path: &Path) -> Result<Library> {
+        let conn = Connection::open_with_flags(
+            db_path,
+            rusqlite::OpenFlags::SQLITE_OPEN_READ_ONLY
+                | rusqlite::OpenFlags::SQLITE_OPEN_NO_MUTEX
+                | rusqlite::OpenFlags::SQLITE_OPEN_URI,
+        )?;
+        Ok(Library {
+            conn: Mutex::new(conn),
+        })
+    }
+