template-engine-copier skill: initial import

Copier + Jinja template-repository design skill: reference architecture,
implementation workflow, validation checklist, and a full worked example
template (questionnaire, extensions, resolvers, wrapper-first .scripts).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

example/.copier/extensions/resolvers/resolve_safe_identifier.py

@@ -0,0 +1,17 @@
+from jinja2.ext import Extension
+
+
+def resolve_safe_identifier(name: str) -> str:
+    return (
+        name
+        .replace("-", "_")
+        .replace("{", "")
+        .replace("}", "")
+        .replace(".", "_")
+    )
+
+
+class SafeIdentifierExtension(Extension):
+    def __init__(self, environment):
+        super().__init__(environment)
+        environment.globals["resolve_safe_identifier"] = resolve_safe_identifier