fix: distinguish probe failure from false in keychain diagnostic

Probes for aliasPresent, entryPresent and walletIndex previously
collapsed any exception inside runCatching to the default value,
making a keystore subsystem / DataStore / Room error indistinguishable
from a legitimate 'alias missing'. Render tri-state instead:
'true' / 'false' / 'error:ClassName'.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jvsena42

app/src/main/java/to/bitkit/data/keychain/Keychain.kt

@@ -143,11 +143,11 @@ class Keychain @Inject constructor(
     private fun emitLoadDiagnosticsOnce(key: String, cause: Throwable) {
         if (!loadDiagnosticsEmitted.add(key)) return
 
-        val aliasPresent = runCatching { keyStore.containsAlias() }.getOrDefault(false)
-        val entryPresent = runCatching { snapshot.contains(key.indexed) }.getOrDefault(false)
-        val walletIndex = runCatching {
+        val aliasPresent = probe { keyStore.containsAlias() }
+        val entryPresent = probe { snapshot.contains(key.indexed) }
+        val walletIndex = probe {
             runBlocking { db.configDao().getAll().first() }.firstOrNull()?.walletIndex ?: 0L
-        }.getOrDefault(-1L)
+        }
         val causeChain = generateSequence(cause) { it.cause }
             .take(CAUSE_CHAIN_DEPTH)
             .joinToString(separator = " <- ") { it.javaClass.simpleName }
@@ -160,6 +160,12 @@ class Keychain @Inject constructor(
         )
     }
 
+    private inline fun <T> probe(block: () -> T): String =
+        runCatching(block).fold(
+            onSuccess = { it.toString() },
+            onFailure = { "error:${it.javaClass.simpleName}" },
+        )
+
     enum class Key {
         PUSH_NOTIFICATION_TOKEN,
         PUSH_NOTIFICATION_PRIVATE_KEY,