Fix stale docs claiming web persistence is in-memory only

Web actually persists via localStorage (LocalStorageStores.kt), which
survives page reloads — only SQLDelight itself isn't used there, since
its web driver needs a worker plus a wasm sqlite binary. The doc
comments and AGENTS.md still described the in-memory state this
replaced.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FXcrACM5sok3M1KQJ8kByy

AGENTS.md

@@ -12,12 +12,9 @@ and Android (see README's Supported Platforms/Download and Install). Web and
 Desktop/JVM are real future release targets too — `desktopApp` already has
 full native packaging configured (DMG/MSI/DEB, see its `build.gradle.kts`) —
 but neither has a release/CI pipeline set up yet, so treat them as
-not-yet-shipped rather than dev-only. Web specifically also has no real
-persistence yet (see `data/db/SqlDelightStores.kt`'s doc comment: no
-SQLDelight driver, in-memory only, nothing survives a page reload) — worth
-keeping in mind if that platform's release plans firm up. The app converts
-between BTC, Sats, and fiat currencies using live exchange rates (Coinbase,
-CoinGecko, or a manually typed-in rate).
+not-yet-shipped rather than dev-only. The app converts between BTC, Sats,
+and fiat currencies using live exchange rates (Coinbase, CoinGecko, or a
+manually typed-in rate).
 
 This is a from-scratch rewrite of an earlier Skip-based (Swift-transpiled-to-
 Kotlin) implementation — `main` is now this Kotlin Multiplatform project.
@@ -146,9 +143,11 @@ to call.
 SQLDelight (`data/db/SqlDelightStores.kt` + platform-specific driver
 `actual`s) backs `ExchangeRateStore`/`SelectedCurrenciesStore`/
 `SelectedSourceStore`, each exposed via an `expect fun createXStore()`
-factory. Web has no real SQLDelight driver — it gets an in-memory-only
-fallback (nothing persists across a page reload). This is a known gap to
-close if/when Web's release plans firm up, not a permanent design choice.
+factory. Web has no real SQLDelight driver — SQLDelight's web driver needs a
+worker plus a wasm sqlite binary — so it gets a `localStorage`-backed
+fallback instead (`data/db/LocalStorageStores.kt`), which does survive page
+reloads, just scoped to the browser profile/origin (cleared by clearing
+site data, not shared across browsers/devices).
 
 ## Testing and verification
 

shared/src/commonMain/kotlin/xyz/tyiu/satsprice/data/db/SqlDelightStores.kt

@@ -10,8 +10,8 @@ import kotlin.time.Instant
 /**
  * Shared by every platform that opens a real [AppDatabase] (Android, Desktop, iOS/macOS) — only
  * driver construction differs per platform, so that's the only expect/actual boundary needed.
- * Web isn't a shipped platform (see README's Supported Platforms) and gets an in-memory fallback
- * instead of a real driver.
+ * Web has no real SQLDelight driver and uses a `localStorage`-backed fallback instead (see
+ * `LocalStorageStores.kt`).
  */
 internal class SqlDelightExchangeRateStore(private val database: AppDatabase) : ExchangeRateStore {
     override suspend fun loadLastKnownRates(sourceId: String): ExchangeRates? = withContext(Dispatchers.Default) {

shared/src/webMain/kotlin/xyz/tyiu/satsprice/data/db/LocalStorageStores.kt

@@ -10,10 +10,11 @@ import xyz.tyiu.satsprice.data.ExchangeRates
 import kotlin.time.Instant
 
 /**
- * Web isn't a shipped platform (see README's Supported Platforms) and SQLDelight's web driver
- * needs a worker plus a wasm sqlite binary, so persistence here goes through the browser's
- * localStorage instead of a real database — plenty for this small amount of data, and it
- * survives page reloads unlike the in-memory state it replaced.
+ * SQLDelight's web driver needs a worker plus a wasm sqlite binary, so persistence here goes
+ * through the browser's localStorage instead of a real database — plenty for this small amount
+ * of data, and it survives page reloads like the other platforms' real databases do. Scoped to
+ * the browser profile/origin, though: it won't survive a cleared site data / private window, and
+ * doesn't sync or back up anywhere.
  */
 private val json = Json { ignoreUnknownKeys = true }