chore(db): drop branch migrations ahead of staging merge

0264/0265 on this branch collide with staging's 0264-0270 on both the
journal idx slots and the meta snapshot filenames. Reverting the migration
artifacts to the merge-base lets staging's chain merge cleanly; schema.ts
keeps the copilot changes and drizzle-kit regenerates a single migration on
top of 0270 after the merge.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: icecrasher321