- `finite_numbers::<N>` (cmd/mod.rs) reads an array of exactly N finite
numbers, nothing dropped or padded; `rect` uses it, and the rect cut,
Free Distort and anchor handles reuse it in the PRs stacked on this one.
- `at` is parsed once (`at_param`) instead of point_param plus a second
shape check that indexed the params; `at: null` means no position, as
null does for the other optional params, and gets a test.
- rustfmt.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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