Establish pass compatibility fixture harness (#1)

crates/storage/tests/fixtures/compatibility/layouts.toml

@@ -0,0 +1,51 @@
+format = 1
+
+[[layout]]
+id = "basic"
+store = "stores/basic"
+purpose = "ordinary, Unicode, OTP, nested recipient, signature, and multi-recipient entries"
+
+[[layout]]
+id = "nested"
+store = "stores/nested/outer"
+purpose = "an outer store and an inner recipient/Git boundary"
+
+[[synthetic_node]]
+layout = "hostile"
+kind = "symlink"
+path = "escape.gpg"
+target = "../outside.gpg"
+expected = "reject-symlink-escape"
+
+[[synthetic_node]]
+layout = "hostile"
+kind = "symlink"
+path = "directory-link"
+target = "../outside"
+expected = "reject-symlink-escape"
+
+[[synthetic_node]]
+layout = "hostile"
+kind = "fifo"
+path = "unsupported.gpg"
+target = ""
+expected = "reject-unsupported-file-type"
+
+[[synthetic_node]]
+layout = "collision"
+kind = "entry-directory-collision"
+path = "ambiguous"
+target = "ambiguous.gpg"
+expected = "require-trailing-slash-disambiguation"
+
+[[interruption]]
+id = "before-temp-fsync"
+expected = "original-entry-intact"
+
+[[interruption]]
+id = "after-temp-fsync-before-rename"
+expected = "original-entry-intact"
+
+[[interruption]]
+id = "after-rename-before-directory-fsync"
+expected = "new-entry-complete"