Studio CSV import: skip type mismatched rows and download rejects

[seandmill]

Problem

In the Table Editor --> Insert --> Import data from CSV flow, a single cell that can't cast to the specified column type fails the whole import (e.g. $99.95 into a float8).

Proposal

Add an opt-in toggle in the import configuration: Skip rows with type mismatches (default off).

When enabled:

1. Client-side validates each row against the target table's column types
2. Insert only valid rows (still batched)
3. After import, show X imported, Y skipped and offer download skipped rows (csv of skipped cells and a skip_reason column)

Why

• Doesn't fabricate or corrupt data (no silent NULL for bad data)
• Avoids brittle transforms in studio
• Puts cleanup onus on the user with a clear reject file