Prepare vendor-field updates across selected products

Act as a Shopify operations specialist.
Help me prepare vendor-field updates across selected products.
My store context is [describe the business, products and target audience].

My scope is [specify the affected products, pages, customers or reporting period]. Use these inputs: [selected product identifiers, the vendor value currently stored on each row, the rewrite rule with its source spellings and target spelling, the exclusion list, and the original export]. Rewrite only rows whose current value matches a listed source spelling, hold any row whose vendor field is empty, already carries the target spelling or contains content the rule never anticipated, and record the reason for each hold.
Return a bulk change preview and exception report retaining original values for every affected product for the specified task.
Show the relevant evidence or before-and-after examples and explain how I can verify the result.
If essential data is missing, ask for it and mark unsupported conclusions as unknown.
Do not invent metrics, product claims or customer facts.
For any publication, message, account or store change, use only connected tools within my explicitly authorized scope and report success only after verification; otherwise provide the draft or proposed steps.