[gen2-migration] Pre-flight validation should name the specific table(s) failing the DeletionProtectionEnabled check

## Summary
Import validation checks `DeletionProtectionEnabled` on source tables, but when one table fails, the result is an opaque whole-data-stack failure with no indication of which table is non-compliant.

## Expected
A pre-flight validation step that names the specific table(s) failing the `DeletionProtectionEnabled` check, before any deploy is attempted — independent of the enable/disable logic itself.

## Type
Enhancement (usability / diagnostics)

Start by locating the Gen 2 migration import pre-flight validation and the DeletionProtectionEnabled check. Trace how validation failures are reported before deployment, then verify that failures identify each non-compliant source table without changing the enable/disable logic.

Written by the indexing model from the issue text.