chore: add .editorconfig and fix lint-on-edit hook

- Add .editorconfig with indent_style=space for .sh files so shfmt
  and git-diff-check no longer conflict on tab indentation
- Replace tab indentation with 2-space indentation in lint-on-edit.sh
- Scope PostToolUse hook to check only the edited file (tool_input.path)
  instead of all git-modified files, reducing unnecessary trunk runs

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: ss-o

.editorconfig

@@ -0,0 +1,26 @@
+# EditorConfig: https://editorconfig.org
+root = true
+
+[*]
+charset = utf-8
+end_of_line = lf
+indent_size = 2
+indent_style = space
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.{md,mdx}]
+trim_trailing_whitespace = false
+
+[*.sh]
+indent_size = 2
+indent_style = space
+
+[*.{json,jsonc}]
+indent_size = 2
+
+[*.{yml,yaml}]
+indent_size = 2
+
+[Makefile]
+indent_style = tab

.github/hooks/lint-on-edit.sh

@@ -13,6 +13,11 @@ tool_name=$(echo "$input" | jq -r '.tool_name // empty')
 
 case "$tool_name" in
 apply_patch | create_file | edit | editFiles | insert_edit_into_file | multi_replace_string_in_file | replace_string_in_file)
-  pnpm lint 2>&1 | tail -40
+  file_path=$(echo "$input" | jq -r '.tool_input.path // empty')
+  if [[ -n $file_path && -f $file_path ]]; then
+    trunk check "$file_path" 2>&1 | tail -40
+  else
+    pnpm lint 2>&1 | tail -40
+  fi
   ;;
 esac