fix: wrap malformed query scalar values in SerializationException

[OmarAlJarrah]

Summary

• QueryDecoder's scalar decoders (decodeInt/decodeLong/decodeShort/decodeByte/decodeDouble/decodeFloat/decodeChar) converted the raw query string directly with toInt()/toLong()/single() etc., so a malformed value let the raw JVM/stdlib exception (NumberFormatException, NoSuchElementException, IllegalArgumentException) escape decodeFromQueryParameters instead of the SerializationException the format's enum-decoding path and the Url/Uri serializers already guarantee.
• A caller wrapping decode in try { ... } catch (e: SerializationException) — the documented pattern for validating untrusted query input — would not catch these.
• Switched each conversion to the *OrNull stdlib variant and fail with a descriptive SerializationException when it returns null, mirroring how the existing enum path resolves an unknown value. Applied to both the top-level QueryDecoder and the list-element QueryListDecoder paths.

Test plan

• Added regression tests in SerdeTest.kt covering malformed Int (page=abc), empty Int, malformed Long/Short/Byte/Double/Float, empty Char, multi-character Char (charValue=ab), and a malformed list element — confirmed each fails before the fix and passes after
• ./gradlew :kuri-serde-kotlinx:jvmTest :kuri-serde-kotlinx:ktlintCheck :kuri-serde-kotlinx:detekt :kuri-serde-kotlinx:apiCheck
• ./gradlew :kuri-serde-kotlinx:jsNodeTest (commonMain touched)
• Not run: wasmJsNodeTest (known to transiently OOM the Kotlin daemon in this environment when bundled with other targets) — unverified on wasm
• No public API shape changed (both decoders are internal), so apiDump was not needed; apiCheck confirms no diff

Closes #83