Dependency-free validation for the common JSON Schema subset used by tools.
The validator supports primitive and union type declarations, required,
recursive properties, additionalProperties, array items, enum,
const, and the usual string, numeric, array, and object size constraints.
Unknown keywords are preserved and ignored, so applications can use this as
a useful baseline while retaining schemas that require a complete backend.
Validation failures return Snodo.Schema.Validator.Basic.Error with a JSON
path and the keyword that rejected the value. The router puts the path and
message, which never quote the value, into the tool's isError result so a
model can correct its call.