libghostty als zweite Terminal-Engine integriert (Default ghostty, SwiftTerm Fallback)

- vendor/libghostty: vorgebaute macOS-libghostty.a (arm64) + Header + Build-Patches + README
- Sources/CGhostty: C-Modul der libghostty-C-API
- Sources/MiniTerm/Ghostty.swift: GhosttyApp + GhosttySurfaceView (Surface, Input, Größe, Fokus)
- main.swift: Engine-Wahl per Info.plist MTEngine
- Package.swift: CGhostty-Target + Link gegen libghostty + Frameworks
- STATUS.md: Stand, Build-Weg (macOS-15-VM), offene Punkte

vendor/libghostty/include/ghostty/vt/result.h

@@ -0,0 +1,22 @@
+/**
+ * @file result.h
+ *
+ * Result codes for libghostty-vt operations.
+ */
+
+#ifndef GHOSTTY_VT_RESULT_H
+#define GHOSTTY_VT_RESULT_H
+
+/**
+ * Result codes for libghostty-vt operations.
+ */
+typedef enum {
+    /** Operation completed successfully */
+    GHOSTTY_SUCCESS = 0,
+    /** Operation failed due to failed allocation */
+    GHOSTTY_OUT_OF_MEMORY = -1,
+    /** Operation failed due to invalid value */
+    GHOSTTY_INVALID_VALUE = -2,
+} GhosttyResult;
+
+#endif /* GHOSTTY_VT_RESULT_H */