feat: Introduce Hashline encoding/validation, implement core REPL and chat session logic, and establish initial project structure with a license and editor configuration.

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 4
+end_of_line = crlf
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.cs]
+dotnet_sort_system_directives_first = true