Reject a synthesised Connection or Edge name that exactly collides with another registered type

Make an exact name collision between a synthesised type and any other registered type a typed rejection at the carrier, instead of a silent last-registration-wins in ConnectionPromoter.registerSynthesised on the schema-transform side and a silently misrouted mint on the capture side. A synthesised type is one @asConnection mints for a carrier field (the field that carries the directive): the <ConnectionName> Connection and <ConnectionName>Edge Edge types.

Today the only collision detector is GraphitronSchemaBuilder.rejectCaseInsensitiveTypeCollisions, which groups registry entries by their case-folded name; an exact collision produces one entry, so its group has size 1 and it is invisible to that detector. Two shapes reach it. A connectionName: override on one carrier that spells another carrier’s derived edge name (connectionName: "QueryFooConnectionEdge" beside a plain Query.foo: [Foo!]! @asConnection) registers a ConnectionType and an EdgeType under one name; TypeRegistry.register demotes the coordinate to UnclassifiedType with a "classified incompatibly" message that names neither carrier. An override spelling an author-declared type’s name registers over it. On the capture side (MacroCapture) the same shapes do not collide but misroute: mintType yields when the coordinate is already claimed, yet the minted fields still land, so cursor and node are written onto whichever type already owns the name.

The intra-carrier instance (an override with no Connection substring, whose edge name equalled its connection name under the substitute formula) is made unreachable by the append formula that ConnectionNaming.defaultEdgeName introduces; this item covers the cross-carrier and synthesised-versus-declared instances that no formula can rule out. The fix wants registerSynthesised to refuse a name already registered under a different GraphitronType arm with a Rejection naming both parties and the carrier coordinate, mirrored by a capture-side detection row so the fact store carries the same verdict, and a validator mirror per the typed-rejection contract in docs/architecture/explanation/typed-rejection.adoc.