Adding "pending" to the settled states bound them as parameters, costing
two bindings on top of one per thread. `--threads` is capped at 32766 —
SQLite's ceiling — so the documented maximum landed exactly two over and
threw "too many SQL variables", after the target had already been
emptied. Inline the literals; they are internal constants, never input.

The regression test seeds at the cap for real rather than asserting the
statement text, since the property is that no code path adds a binding.
Fixture rows are batched into one transaction and the scale case builds
thread rows only, keeping it near a second.

Caught by Macroscope review.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>