Refactor SP-API test script and improve type definitions

- Updated `sp-test.ts` to enhance argument parsing and error handling for sellability checks.
- Refactored `types.ts` to maintain consistent formatting and improve readability.
- Improved `writer.ts` for better result handling and CSV writing, ensuring clarity in output.
- Adjusted `tsconfig.json` formatting for consistency and readability.

.claude/settings.local.json

@@ -1,10 +1,10 @@
-{
-  "permissions": {
-    "allow": [
-      "WebSearch",
-      "Bash(bun init:*)",
-      "Bash(bunx tsc:*)",
-      "Bash(bun -e ':*)"
-    ]
-  }
-}
+{
+  "permissions": {
+    "allow": [
+      "WebSearch",
+      "Bash(bun init:*)",
+      "Bash(bunx tsc:*)",
+      "Bash(bun -e ':*)"
+    ]
+  }
+}