Two defects from the same blind spot: verifying a thing one way and
assuming the other way works.
Trackpad scrolling over the Scene Template Center moved the canvas while
the card grid sat still. Wheel deltas route through `apply_wheel_inner`,
trackpad pans through `apply_pan_gesture` — two ladders — and the panel
was wired into only the first. Every mouse-wheel check passed. The
Prompt Center's own host test already covered both paths; this adds its
twin, which fails without the fix.
The shipped deck template opened as one visible slide with five stacked
underneath it. Its generator never set `x`/`y`, so every board defaulted
to the origin. It went unnoticed because the deck was only ever
inspected through per-frame rendering, which draws each board alone —
the stacking exists solely in the assembled document. `knowledge-carousel`
has laid its frames out since it shipped, so this was breaking an
existing convention rather than lacking one.
The catalogue now asserts that every multi-frame template positions each
frame and that no two share a spot, so the next template cannot repeat
it. Fixed in the generator, not the artefact, so regenerating keeps it.
Claude-Session: https://claude.ai/code/session_01FqKQqNj8exYwopGDpYUU7x
ad2f0e4a6a