android: V4.9 + V4.10 Kotlin ports + KeystoreStorage adapter

Pure-JVM additions to shade-android (no Android SDK needed):
- V4.9 blob primitives: BlobKdf (HKDF deriveBlobSlotId/Key/SigningSeed),
  BlobAead (nonce||ct||tag with shade-profile-aad-v1:<slot> AAD),
  BlobClient (java.net.http with hand-written canonical JSON signing
  matching TS signPayload output), Profile high-level namespace.
- V4.10 approval helpers: CanonicalProfileBlob schema with denormalized
  trustedApproverFingerprints, build/sign/verify proxy approvals via
  length-prefixed u16 BE UTF-8 canonical signing payload.
- Password KDFs: scrypt + argon2id via Bouncy Castle, NFKC-normalized.
- SessionStateJson at-rest serializer for persistence layer.

Cross-platform vectors (test-vectors/blob.json, approval.json) gate
byte-identical output between TS and Kotlin, including a TS-signed
Ed25519 signature the Kotlin port verifies and reproduces (Ed25519 is
deterministic).

New shade-android-keystore sibling Gradle module (Android-specific):
- KeystoreMasterKey: hardware-backed AES-256-GCM with BIOMETRIC_STRONG
  gating, StrongBox-backed when available, invalidated on enrollment.
- BiometricUnlock: coroutine wrapper around BiometricPrompt with
  tagged cancellation/failure exceptions.
- KeystoreStorage: StorageProvider over biometric-gated AES-encrypted
  SharedPreferences with AAD-bound row keys.

All 25 SDK packages typecheck clean; 104 SDK tests + 24 new Kotlin
tests + 11 cross-platform vector tests all green.

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

android/shade-android/src/test/kotlin/no/zyon/shade/SessionStateJsonTest.kt

@@ -0,0 +1,123 @@
+package no.zyon.shade
+
+import no.zyon.shade.serialization.SessionStateJson
+import no.zyon.shade.types.ChainState
+import no.zyon.shade.types.IdentityKeyPair
+import no.zyon.shade.types.KeyPair
+import no.zyon.shade.types.OneTimePreKey
+import no.zyon.shade.types.SessionState
+import no.zyon.shade.types.SignedPreKey
+import org.junit.Assert.assertArrayEquals
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNotNull
+import org.junit.Assert.assertNull
+import org.junit.Test
+
+/**
+ * Round-trip tests for the at-rest JSON serialization used by
+ * `KeystoreStorage`. The format isn't cross-platform (TS uses its
+ * own shape) — what matters is `serialize → deserialize` preserves
+ * every byte of every key.
+ */
+class SessionStateJsonTest {
+
+    private fun bytes(n: Int, fill: Byte): ByteArray = ByteArray(n) { fill }
+
+    @Test
+    fun identityKeyPairRoundTrip() {
+        val k = IdentityKeyPair(
+            signingPublicKey = bytes(32, 0x11),
+            signingPrivateKey = bytes(32, 0x22),
+            dhPublicKey = bytes(32, 0x33),
+            dhPrivateKey = bytes(32, 0x44),
+        )
+        val s = SessionStateJson.serializeIdentityKeyPair(k)
+        val d = SessionStateJson.deserializeIdentityKeyPair(s)
+        assertArrayEquals(k.signingPublicKey, d.signingPublicKey)
+        assertArrayEquals(k.signingPrivateKey, d.signingPrivateKey)
+        assertArrayEquals(k.dhPublicKey, d.dhPublicKey)
+        assertArrayEquals(k.dhPrivateKey, d.dhPrivateKey)
+    }
+
+    @Test
+    fun signedPreKeyRoundTrip() {
+        val k = SignedPreKey(
+            keyId = 42,
+            keyPair = KeyPair(publicKey = bytes(32, 0x55), privateKey = bytes(32, 0x66)),
+            signature = bytes(64, 0x77),
+            timestamp = 1_700_000_000_000L,
+        )
+        val s = SessionStateJson.serializeSignedPreKey(k)
+        val d = SessionStateJson.deserializeSignedPreKey(s)
+        assertEquals(k.keyId, d.keyId)
+        assertArrayEquals(k.keyPair.publicKey, d.keyPair.publicKey)
+        assertArrayEquals(k.keyPair.privateKey, d.keyPair.privateKey)
+        assertArrayEquals(k.signature, d.signature)
+        assertEquals(k.timestamp, d.timestamp)
+    }
+
+    @Test
+    fun oneTimePreKeyRoundTrip() {
+        val k = OneTimePreKey(
+            keyId = 7,
+            keyPair = KeyPair(publicKey = bytes(32, 0x88.toByte()), privateKey = bytes(32, 0x99.toByte())),
+        )
+        val s = SessionStateJson.serializeOneTimePreKey(k)
+        val d = SessionStateJson.deserializeOneTimePreKey(s)
+        assertEquals(k.keyId, d.keyId)
+        assertArrayEquals(k.keyPair.publicKey, d.keyPair.publicKey)
+        assertArrayEquals(k.keyPair.privateKey, d.keyPair.privateKey)
+    }
+
+    @Test
+    fun sessionStateRoundTripFullPopulated() {
+        val state = SessionState(
+            remoteIdentityKey = bytes(32, 0x01),
+            rootKey = bytes(32, 0x02),
+            sendChain = ChainState(chainKey = bytes(32, 0x03), counter = 5),
+            receiveChain = ChainState(chainKey = bytes(32, 0x04), counter = 3),
+            dhSend = KeyPair(publicKey = bytes(32, 0x05), privateKey = bytes(32, 0x06)),
+            dhReceive = bytes(32, 0x07),
+            previousSendCounter = 9,
+            skippedKeys = mutableMapOf(
+                "remote:1" to bytes(32, 0x0A),
+                "remote:2" to bytes(32, 0x0B),
+            ),
+        )
+        val s = SessionStateJson.serialize(state)
+        val d = SessionStateJson.deserialize(s)
+        assertArrayEquals(state.remoteIdentityKey, d.remoteIdentityKey)
+        assertArrayEquals(state.rootKey, d.rootKey)
+        assertArrayEquals(state.sendChain.chainKey, d.sendChain.chainKey)
+        assertEquals(state.sendChain.counter, d.sendChain.counter)
+        assertNotNull(d.receiveChain)
+        assertArrayEquals(state.receiveChain!!.chainKey, d.receiveChain!!.chainKey)
+        assertArrayEquals(state.dhSend.publicKey, d.dhSend.publicKey)
+        assertArrayEquals(state.dhSend.privateKey, d.dhSend.privateKey)
+        assertArrayEquals(state.dhReceive, d.dhReceive)
+        assertEquals(state.previousSendCounter, d.previousSendCounter)
+        assertEquals(state.skippedKeys.size, d.skippedKeys.size)
+        for ((k, v) in state.skippedKeys) {
+            assertArrayEquals(v, d.skippedKeys[k])
+        }
+    }
+
+    @Test
+    fun sessionStateRoundTripWithNullableFields() {
+        val state = SessionState(
+            remoteIdentityKey = bytes(32, 0x01),
+            rootKey = bytes(32, 0x02),
+            sendChain = ChainState(chainKey = bytes(32, 0x03), counter = 0),
+            receiveChain = null,
+            dhSend = KeyPair(publicKey = bytes(32, 0x05), privateKey = bytes(32, 0x06)),
+            dhReceive = null,
+            previousSendCounter = 0,
+            skippedKeys = mutableMapOf(),
+        )
+        val s = SessionStateJson.serialize(state)
+        val d = SessionStateJson.deserialize(s)
+        assertNull(d.receiveChain)
+        assertNull(d.dhReceive)
+        assertEquals(0, d.skippedKeys.size)
+    }
+}