fix(quartz/sqlite): serialise writes via a Room-style connection pool

androidx.sqlite SQLiteConnection is not thread-safe; SQLiteEventStore
shared a single lazy connection across all callers, so two coroutines
calling insertEvent() at the same time would race on BEGIN IMMEDIATE
and the modules' prepared statements, surfacing as
"cannot start a transaction within a transaction" or SQLITE_MISUSE.

Mirror Room's design: introduce SQLiteConnectionPool with one writer
connection guarded by a coroutine Mutex and N reader connections
handed out via a Channel-as-semaphore (file-backed DBs only; in-memory
DBs share the writer because each ":memory:" connection is a separate
DB). Convert IEventStore + SQLiteEventStore + EventStore + FsEventStore
+ LiveEventStore to suspend, route writes through useWriter and reads
through useReader. RelaySession now launches handleEvent / handleCount
on its scope. CLI Context helpers and StoreCommands.sweepExpired pick
up suspend.

Add ParallelInsertTest to lock the behaviour in: 8 coroutines × 200
inserts, parallel reads alongside writes, transaction batches across
coroutines, and a reopen smoke test all pass against a file-backed DB.

https://claude.ai/code/session_016b5kSSbtDS3Ead6pN3Xqt5

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip01Core/store/sqlite/AssertUtils.kt

@@ -24,7 +24,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.relay.filters.Filter
 import kotlin.test.assertEquals
 
-fun <T : Event> EventStore.assertQuery(
+suspend fun <T : Event> EventStore.assertQuery(
     expected: T?,
     filter: Filter,
 ) {
@@ -40,7 +40,7 @@ fun <T : Event> EventStore.assertQuery(
     }
 }
 
-fun <T : Event> EventStore.assertQuery(
+suspend fun <T : Event> EventStore.assertQuery(
     expected: List<T>,
     filter: Filter,
 ) {
@@ -53,7 +53,7 @@ fun <T : Event> EventStore.assertQuery(
     }
 }
 
-fun <T : Event> SQLiteEventStore.assertQuery(
+suspend fun <T : Event> SQLiteEventStore.assertQuery(
     expected: T?,
     filter: Filter,
 ) {
@@ -69,7 +69,7 @@ fun <T : Event> SQLiteEventStore.assertQuery(
     }
 }
 
-fun <T : Event> SQLiteEventStore.assertQuery(
+suspend fun <T : Event> SQLiteEventStore.assertQuery(
     expected: List<T>,
     filter: Filter,
 ) {

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip01Core/store/sqlite/BasicTest.kt

@@ -307,10 +307,14 @@ class BasicTest : BaseDBTest() {
             // modules.forEach { it.create(db) }. Pre-fix, FullTextSearchModule
             // left dummy_fts3/4/5 tables behind on first probe, so the
             // second create() would throw "already exists".
-            db.store.modules
-                .reversed()
-                .forEach { it.drop(db.store.connection) }
-            db.store.modules.forEach { it.create(db.store.connection) }
+            // Drive the module re-create against the writer connection
+            // (drop + create touches schema, so we need exclusive access).
+            db.store.pool.useWriter { conn ->
+                db.store.modules
+                    .reversed()
+                    .forEach { it.drop(conn) }
+                db.store.modules.forEach { it.create(conn) }
+            }
 
             // After re-creation the store is still usable.
             val note = signer.sign(TextNoteEvent.build("test1"))

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip01Core/store/sqlite/LargeDBTests.kt

@@ -26,6 +26,7 @@ import com.vitorpamplona.quartz.nip01Core.core.Event
 import com.vitorpamplona.quartz.nip01Core.core.OptimizedJsonMapper
 import com.vitorpamplona.quartz.nip40Expiration.isExpired
 import com.vitorpamplona.quartz.utils.Log
+import kotlinx.coroutines.runBlocking
 import kotlin.test.AfterTest
 import kotlin.test.BeforeTest
 import kotlin.test.Test
@@ -56,24 +57,26 @@ class LargeDBTests {
     }
 
     @Test
-    fun insertHeavyEvent() {
-        events.first { it.id == "3f34b8cb682307ec11753de4669ce8948e95fd6fb360d79136446c5547fd235e" }.let { event ->
-            try {
-                db.insert(event)
-            } catch (e: SQLiteException) {
-                Log.w("LargeDBTests") { "Error inserting event: ${e.message} for event: ${event.toJson()}" }
+    fun insertHeavyEvent() =
+        runBlocking {
+            events.first { it.id == "3f34b8cb682307ec11753de4669ce8948e95fd6fb360d79136446c5547fd235e" }.let { event ->
+                try {
+                    db.insert(event)
+                } catch (e: SQLiteException) {
+                    Log.w("LargeDBTests") { "Error inserting event: ${e.message} for event: ${event.toJson()}" }
+                }
             }
         }
-    }
 
     @Test
-    fun insertDatabase() {
-        events.forEach { event ->
-            try {
-                db.insert(event)
-            } catch (e: SQLiteException) {
-                Log.w("LargeDBTests") { "Error inserting event: ${e.message} for event: ${event.toJson()}" }
+    fun insertDatabase() =
+        runBlocking {
+            events.forEach { event ->
+                try {
+                    db.insert(event)
+                } catch (e: SQLiteException) {
+                    Log.w("LargeDBTests") { "Error inserting event: ${e.message} for event: ${event.toJson()}" }
+                }
             }
         }
-    }
 }

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nip01Core/store/sqlite/QueryAssemblerTest.kt

@@ -37,9 +37,9 @@ class QueryAssemblerTest : BaseDBTest() {
     val key2 = "f3ac434d61bc0f491a814782ccfdf9c439dae1f0bde9097ad4a245f4c495cd14"
     val key3 = "12ae0fd81c85e1e7d9ed096397dc3129849425fe6f8afce7213ebf38ddfc6ca9"
 
-    fun EventStore.explain(f: Filter) = store.queryBuilder.planQuery(f, hasher, store.connection)
+    suspend fun EventStore.explain(f: Filter) = store.pool.useReader { store.queryBuilder.planQuery(f, hasher, it) }
 
-    fun EventStore.explain(f: List<Filter>) = store.queryBuilder.planQuery(f, hasher, store.connection)
+    suspend fun EventStore.explain(f: List<Filter>) = store.pool.useReader { store.queryBuilder.planQuery(f, hasher, it) }
 
     @Test
     fun testEmpty() =