feat: add validation tooling and expand path review instructions

Add pre-commit hooks (YAML lint, schema validation, editorconfig),
CI workflow, and new path instructions for test files, Dockerfiles,
config files, and archival docs.

.editorconfig

@@ -0,0 +1,15 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+indent_size = 2
+
+[*.md]
+trim_trailing_whitespace = false
+
+[Makefile]
+indent_style = tab