feat: implement Ghidra adapter and Nix integration

fixtures/README.md

@@ -0,0 +1,14 @@
+# Reproducible native fixtures
+
+`fixtures/src/known.c` is compiled by Nix into two tiny, dependency-free test
+programs from the same reviewed source:
+
+- `elf-x86_64/known.elf`: static ELF, x86-64 little-endian;
+- `pe32plus-x86_64/known.exe`: PE32+, x86-64.
+
+Both builds disable timestamps and build IDs, set `SOURCE_DATE_EPOCH=1`, avoid
+host libraries, and are stripped only of non-semantic comments/notes. Build
+them with `nix build .#fixtures`. Version 0.1 intentionally does not claim an
+unverified third target until that target is exercised by the real-Ghidra
+suite; recognizing a file format without a maintained cross-toolchain test is
+not sufficient evidence.