Copilot round 7: both findings are the same principle applied one level
further — JSON Schema siblings are conjunctive, and this code was treating
them as alternatives.
1. The hoist is a spread, so a branch keyword *replaced* the wrapper's. That
is not a conjunction: a wrapper `enum: ["a"]` around a branch
`enum: ["a", "b"]` means `"a"`, but the spread produced `["a", "b"]` and
the dropdown would have offered — and submitted — a `"b"` the schema
rejects. `type`, bounds, and the object keywords fail the same way.
The collapse now declines when wrapper and branch carry different values
for the same validation keyword, and the field renders through the JSON
editor with its schema intact. Intersecting them properly is a much larger
surface, and a subtly wrong intersection would be worse than none.
Identical values are not a conflict, so the ordinary redundant-`type`
shape still collapses; metadata (`title`, `description`, `default`,
`enumNames`) never conflicts, since nothing validates against it.
2. `admitsNull` let a `{ type: "null" }` branch outvote an explicit
non-null top-level `type`. `{ type: "string", anyOf: [..., { type:
"null" }] }` rejects null — the value must satisfy the type *and* the
union — so an explicit `type` now decides instead of falling through to
the branch scan.
Signed-off-by: cliffhall <cliff@futurescale.com>