Same fix #1383 applied to the Job table's antijoin in refresh(),
now applied to AutoPopulate._populate_direct's antijoin and the
progress() fallback path. The two-arg subtract `key_source - self`
triggers QueryExpression.__sub__ which calls .restrict(Not(...))
with semantic_check=True by default.

The semantic-check requirement is wrong here: this antijoin is a
plain set-difference, not a join — we ask "which key_source rows
aren't yet in self." Whether the same-named PK attribute carries
the same source-table lineage tag on both sides is irrelevant.

Where it bites: dj.Imported / dj.Computed tables whose primary key
is fully inherited from a single FK, with no own-table PK attributes.
On those, self.proj() returns the PK attribute with lineage=None
(or pointing to self rather than the FK parent), while key_source's
matching attribute carries the parent's lineage tag. The
semantic-check fails with:

    Cannot join on attribute 'X': different lineages
    (schema.parent.X vs None). Use .proj() to rename one of the
    attributes.

This pattern is legitimate ("one row downstream per parent row,
no intermediate ID") but rare in typical Elements / SciOps pipelines,
which extend the inherited PK with own-table attributes (trial_id,
experiment_id, etc.) that anchor proj()'s lineage. That's why the
existing #1405 test suite didn't surface it.

Changes:
- src/datajoint/autopopulate.py
  - Import Not from .condition at module top.
  - _populate_direct: replace `(LHS - self.proj())` with
    `LHS.restrict(Not(self.proj()), semantic_check=False)`.
  - progress(): same swap on the no-common-attrs fallback branch.
- tests/integration/test_autopopulate.py
  - New test_populate_antijoin_fk_inherited_pk regression test:
    Spec(Manual) -> Item(Imported with only -> Spec) — the minimal
    shape that triggers the bug. Without the fix Item.populate()
    raises DataJointError; with the fix it populates correctly,
    progress() reports correct counts, and partial-then-full
    populate works.

Stacked on top of #1452 (the secrets-loading + dead-code fix); rebase
to master after that lands.