### Fixed
- `slot(name, def)` now correctly warns if no slot or default is found.
- Default slot fallback parsing now returns consistent `<template>` elements.
- Internal devtools spy restored after each test for console warnings.

### Added
- New test: `SlotWarning.test.js` to ensure slot warnings and fallback work.
- Improved test suite coverage for `Computed`, `BusState`, `BoolAttrEffect`.