chore: bootstrap repository tooling

Add npm and Bun dependency metadata.

Configure TypeScript and shared editor defaults.

Ignore dependencies, build output, caches, logs, and local files.

.editorconfig

@@ -0,0 +1,14 @@
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 2
+indent_style = space
+insert_final_newline = true
+trim_trailing_whitespace = true
+max_line_length = 120
+tab_width = 2
+
+[*.{json,md}]
+insert_final_newline = false