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

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/Context.kt

@@ -173,7 +173,7 @@ class Context(
      * publish from", which mirrors `User.outboxRelays()` in the
      * Android app.
      */
-    fun outboxRelays(): Set<NormalizedRelayUrl> =
+    suspend fun outboxRelays(): Set<NormalizedRelayUrl> =
         relaysOf(identity.pubKeyHex)?.writeRelaysNorm()?.takeIf { it.isNotEmpty() }?.toSet()
             ?: DefaultNIP65RelaySet
 
@@ -181,7 +181,7 @@ class Context(
      * DM inbox relays (NIP-17 kind:10050) for this account. Falls back
      * to [DefaultDMRelayList] when no kind:10050 has been seen.
      */
-    fun inboxRelays(): Set<NormalizedRelayUrl> =
+    suspend fun inboxRelays(): Set<NormalizedRelayUrl> =
         dmInboxOf(identity.pubKeyHex)?.relays()?.takeIf { it.isNotEmpty() }?.toSet()
             ?: DefaultDMRelayList.toSet()
 
@@ -190,12 +190,12 @@ class Context(
      * back to [outboxRelays] when no kind:10051 has been seen — same
      * fallback the Android app uses for KeyPackage discovery.
      */
-    fun keyPackageRelays(): Set<NormalizedRelayUrl> =
+    suspend fun keyPackageRelays(): Set<NormalizedRelayUrl> =
         keyPackageRelaysOf(identity.pubKeyHex)?.relays()?.takeIf { it.isNotEmpty() }?.toSet()
             ?: outboxRelays()
 
     /** Union of all three buckets. */
-    fun anyRelays(): Set<NormalizedRelayUrl> = outboxRelays() + inboxRelays() + keyPackageRelays()
+    suspend fun anyRelays(): Set<NormalizedRelayUrl> = outboxRelays() + inboxRelays() + keyPackageRelays()
 
     /**
      * Seed relays for "look up someone we know nothing about" queries —
@@ -208,7 +208,7 @@ class Context(
      * most reliable place to find a stranger's replaceable events even when
      * we and they have completely disjoint relay configurations.
      */
-    fun bootstrapRelays(): Set<NormalizedRelayUrl> =
+    suspend fun bootstrapRelays(): Set<NormalizedRelayUrl> =
         buildSet {
             addAll(anyRelays())
             addAll(DefaultNIP65RelaySet)
@@ -319,7 +319,7 @@ class Context(
      * Every event-arrival path in the CLI funnels through this method
      * so that [store] is the authoritative cache of what Amy has seen.
      */
-    fun verifyAndStore(event: Event): Boolean {
+    suspend fun verifyAndStore(event: Event): Boolean {
         if (!event.verify()) {
             System.err.println("[cli] dropped event ${event.id.take(8)} kind=${event.kind} — bad signature")
             return false
@@ -342,7 +342,7 @@ class Context(
      * this user. Callers that need a network fetch on miss should fall
      * back to [drain] explicitly — this helper never hits the network.
      */
-    fun profileOf(pubKey: HexKey): MetadataEvent? =
+    suspend fun profileOf(pubKey: HexKey): MetadataEvent? =
         store
             .query<Event>(
                 Filter(authors = listOf(pubKey), kinds = listOf(MetadataEvent.KIND), limit = 1),
@@ -352,7 +352,7 @@ class Context(
      * Latest known kind:10002 advertised relay list (NIP-65) for
      * [pubKey]. `null` when Amy has never seen one.
      */
-    fun relaysOf(pubKey: HexKey): AdvertisedRelayListEvent? =
+    suspend fun relaysOf(pubKey: HexKey): AdvertisedRelayListEvent? =
         store
             .query<Event>(
                 Filter(authors = listOf(pubKey), kinds = listOf(AdvertisedRelayListEvent.KIND), limit = 1),
@@ -363,7 +363,7 @@ class Context(
      * `null` if Amy has never observed one. Useful for follow-graph
      * lookups without re-hitting relays.
      */
-    fun contactsOf(pubKey: HexKey): ContactListEvent? =
+    suspend fun contactsOf(pubKey: HexKey): ContactListEvent? =
         store
             .query<Event>(
                 Filter(authors = listOf(pubKey), kinds = listOf(ContactListEvent.KIND), limit = 1),
@@ -374,7 +374,7 @@ class Context(
      * for [pubKey], or `null` if Amy has never observed one. Used by
      * `dm send` to resolve where to deliver a wrap.
      */
-    fun dmInboxOf(pubKey: HexKey): ChatMessageRelayListEvent? =
+    suspend fun dmInboxOf(pubKey: HexKey): ChatMessageRelayListEvent? =
         store
             .query<Event>(
                 Filter(authors = listOf(pubKey), kinds = listOf(ChatMessageRelayListEvent.KIND), limit = 1),
@@ -386,7 +386,7 @@ class Context(
      * `marmot key-package check` and `marmot await key-package` to
      * locate where the recipient publishes their KeyPackages.
      */
-    fun keyPackageRelaysOf(pubKey: HexKey): KeyPackageRelayListEvent? =
+    suspend fun keyPackageRelaysOf(pubKey: HexKey): KeyPackageRelayListEvent? =
         store
             .query<Event>(
                 Filter(authors = listOf(pubKey), kinds = listOf(KeyPackageRelayListEvent.KIND), limit = 1),
@@ -405,7 +405,7 @@ class Context(
      * we'll still hand back the old list. Commands that care can drain
      * (which re-populates the cache) or expose a `--refresh` flag.
      */
-    fun cachedRelayListsOf(pubKey: HexKey): RecipientRelayFetcher.Lists? {
+    suspend fun cachedRelayListsOf(pubKey: HexKey): RecipientRelayFetcher.Lists? {
         val dm = dmInboxOf(pubKey)
         val kp = keyPackageRelaysOf(pubKey)
         val nip65 = relaysOf(pubKey)

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/commands/FeedCommand.kt

@@ -142,7 +142,7 @@ object FeedCommand {
      * an arbitrary `--author` we have no idea where they publish, so we
      * widen to the bootstrap union.
      */
-    private fun relaysForReadingFeed(
+    private suspend fun relaysForReadingFeed(
         ctx: Context,
         mode: String,
     ): Set<NormalizedRelayUrl> =

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/commands/ProfileCommands.kt

@@ -226,7 +226,7 @@ object ProfileCommands {
      * else's profile, fall back to the bootstrap union so we still find a
      * kind:0 even when our relay set and theirs are disjoint.
      */
-    private fun relaysForReadingProfile(
+    private suspend fun relaysForReadingProfile(
         ctx: Context,
         isSelf: Boolean,
     ): Set<NormalizedRelayUrl> =

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/commands/RelayCommands.kt

@@ -137,7 +137,7 @@ object RelayCommands {
         }
     }
 
-    private fun list(dataDir: DataDir): Int {
+    private suspend fun list(dataDir: DataDir): Int {
         val ctx = Context.open(dataDir)
         try {
             val self = ctx.identity.pubKeyHex

cli/src/main/kotlin/com/vitorpamplona/amethyst/cli/commands/StoreCommands.kt

@@ -132,7 +132,7 @@ object StoreCommands {
         return 0
     }
 
-    private fun sweepExpired(dataDir: DataDir): Int =
+    private suspend fun sweepExpired(dataDir: DataDir): Int =
         withStore(dataDir) { store ->
             val expiresAtDir = dataDir.eventsDir.toPath().resolve("idx/expires_at")
             val before = countEntries(expiresAtDir)