"""ui_settings: the 9th identity color — grid_line (phase 92, task 01)

Revision ID: 0015
Revises: 0014
Create Date: 2026-09-09

Phase 92 (the theme controls drive the ENTIRE site — the owner's
defect report: "the background grid never changes color"): the
background grid texture becomes the 9th tab-controlled IDENTITY
variable, so it flows through the resolver, the pre-paint tag, the
CSP hash, and the admin API exactly like the existing 8 (all of those
are ``COLOR_FIELDS``-driven — zero logic changes):

* ``ui_settings.grid_line`` — VARCHAR(7) NULL ``#rrggbb`` (NULL = the
  built-in ``#4a2626`` — today's hardcoded grid color, exact). ONE
  additive, fully reversible column on the single-row table (A13).
"""
from __future__ import annotations

import sqlalchemy as sa

from alembic import op

revision = "0015"
down_revision = "0014"
branch_labels = None
depends_on = None


def upgrade() -> None:
    op.add_column(
        "ui_settings", sa.Column("grid_line", sa.String(length=7), nullable=True)
    )


def downgrade() -> None:
    # Safe order: the column is the only 0015 artefact — dropping it
    # leaves 0014's schema byte-identical (A13, fully reversible).
    op.drop_column("ui_settings", "grid_line")