Tidy and dedupe a contact export while keeping every real record

Clean and deduplicate [path to export.csv], a [HubSpot / Salesforce / other] export of [contacts / companies], about [N] rows.
Work on a copy. Never change or delete the original file.

1. Profile the file with code: row count, columns, blanks per column, encoding, delimiter, date formats found, and the 10 most common values in [country, company, owner]. Show me the profile and stop.

After I confirm:
2. Normalise in NEW columns, keep the originals: email (trim, lowercase), phone (E.164 using default country [US]), first and last name (trim, fix case), company (trim, drop "Inc", "Ltd" only in the match column), dates (ISO). If a date is ambiguous, such as 05/07, do not guess. Flag it.
3. Exact duplicates: group rows with the same normalised [email]. Within a group keep [the most recently updated row] and fill its blank fields from the others. Never overwrite a non-blank value. Record every merge in a change log: kept row id, removed row ids, fields filled.
4. Possible duplicates: find pairs with the same normalised name and the same company or phone, or very similar emails. Do not merge these. Put them in a review sheet with both rows side by side and the reason.
5. Never treat two rows as duplicates when they have different non-blank emails or different non-blank [CRM ids], even if the names match.
6. Reconcile with code: input rows = output rows + rows removed as exact duplicates. Print the numbers. If they do not match, stop.
7. Save clean.csv, changelog.csv and review.csv next to the original. Do not import anything into the CRM.

Hard rules
- All work happens in code. Do not edit rows by hand in the chat.
- Do not delete any file. Do not write to the CRM. Stop and ask me before either.