M-08: relax validateField — allow JSON-escapable control chars, reject only NUL

@@ -56,7 +56,7 @@5656 private const val MAX_RELAY_URL = 20485757 5858 private val PairIdentityJson = Json {59-    encodeDefaults = false59+    encodeDefaults = true6060     ignoreUnknownKeys = true6161 }6262 @@ -111,11 +111,12 @@111111 private fun validateField(value: String, name: String, maxLen: Int) {112112     require(value.isNotEmpty()) { "$name missing" }113113     require(value.length <= maxLen) { "$name exceeds $maxLen chars" }114-    // JSON strings cannot carry raw control bytes; reject them at the trust115-    // boundary so a peer that hands us a name with an embedded NUL or newline116-    // can't truncate the frame even if the encoder slips up.114+    // JSON escapes control chars (newlines, tabs, etc.) as \uXXXX, so legitimate115+    // device names containing them round-trip correctly. Only NUL is universally116+    // problematic — kotlinx.serialization can emit it but parsers downstream117+    // often truncate at it.117118     for (ch in value) {118-        require(ch.code >= 0x20 && ch.code != 0x7f) { "$name contains control character" }119+        require(ch.code != 0x00) { "$name contains NUL" }119120     }120121 }121122