feat: Implement supplier export functionality with workbook generation

- Add `writeSupplierWorkbook` function to create Excel workbooks for supplier analysis results.
- Introduce `SupplierExportSummary` type for summarizing export data.
- Create tests for `writeSupplierWorkbook` to ensure correct sheet creation and data population.
- Implement supplier scoring logic in `supplier-scoring.ts` to evaluate product profitability and demand.
- Add tests for supplier scoring to validate scoring logic and verdict determination.
- Enhance UPC file analysis to integrate supplier scoring and export results to Excel.
- Update database writing logic to accommodate new supplier analysis results.
- Refactor types to include supplier-specific data structures and scoring metrics.
- Ensure proper cleanup of temporary files after tests.

CLAUDE.md

@@ -19,9 +19,15 @@ Default to using Bun instead of Node.js.
 - Prefer `Bun.file` over `node:fs`'s readFile/writeFile
 - Bun.$`ls` instead of execa.
 
-## Testing
-
-Use `bun test` to run tests.
+## Testing
+
+Use `bun test` to run tests.
+
+For this project, also use TypeScript's local compiler for type-checking:
+
+```sh
+./node_modules/.bin/tsc --noEmit
+```
 
 ```ts#index.test.ts
 import { test, expect } from "bun:test";
@@ -103,4 +109,14 @@ Then, run index.ts
 bun --hot ./index.ts
 ```
 
-For more information, read the Bun API docs in `node_modules/bun-types/docs/**.mdx`.
+For more information, read the Bun API docs in `node_modules/bun-types/docs/**.mdx`.
+
+## asin-check Project Notes
+
+- Keep the existing ASIN lead-list and category flows compatible with their current LLM-based FBA/FBM/SKIP analysis.
+- The supplier UPC workflow is deterministic and runs through `bun run upc-file --input input/supplier.xlsx --out output/supplier_ranked.xlsx`.
+- Keep supplier spreadsheets in `input/`, generated workbooks in `output/`, and SQLite files in `db/`; folder contents are ignored by git.
+- Supplier UPC files should resolve UPC/EAN values through SP-API catalog lookup first, with Keepa UPC lookup only as fallback for no-match or request-failure cases.
+- The supplier pipeline should not call LM Studio. It should enrich with Keepa + SP-API sellability/fees, score BUY/WATCH/SKIP numerically, write an Excel workbook, and persist rows to SQLite.
+- Supplier workbook output should keep the `Ranked Leads`, `Skipped`, and `Summary` sheets.
+- When changing UPC supplier behavior, cover SP-API UPC parsing, deterministic scoring, and workbook export with `bun test`.