test(core): Swift oracle — the filius-ipad core built on Linux as the reference

tools/swift-oracle builds the unchanged Swift runtime (pinned 3b5ded0)
in Docker and replays JSON scenarios; the TypeScript engine must produce
the same trace events, results and end state. Five scenarios, 884
events, identical.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/swift-oracle/Sources/Compression/Shim.swift

@@ -0,0 +1,23 @@
+// Linux stand-in for the one call filius-ipad makes into Apple's Compression
+// framework: COMPRESSION_ZLIB is raw DEFLATE (RFC 1951), decoded here by zlib.
+import CZlib
+
+public struct compression_algorithm: Equatable { let rawValue: Int32 }
+public let COMPRESSION_ZLIB = compression_algorithm(rawValue: 0x205)
+
+public func compression_decode_buffer(
+    _ dst: UnsafeMutablePointer<UInt8>, _ dstSize: Int,
+    _ src: UnsafePointer<UInt8>, _ srcSize: Int,
+    _ scratch: UnsafeMutableRawPointer?, _ algorithm: compression_algorithm
+) -> Int {
+    var stream = z_stream()
+    guard inflateInit2_(&stream, -15, ZLIB_VERSION, Int32(MemoryLayout<z_stream>.size)) == Z_OK else { return 0 }
+    defer { inflateEnd(&stream) }
+    stream.next_in = UnsafeMutablePointer(mutating: src)
+    stream.avail_in = uInt(srcSize)
+    stream.next_out = dst
+    stream.avail_out = uInt(dstSize)
+    let status = inflate(&stream, Z_FINISH)
+    guard status == Z_STREAM_END || status == Z_OK || status == Z_BUF_ERROR else { return 0 }
+    return Int(stream.total_out)
+}