Lift ColumnField.parentTable from emitter parameter to record component

Surfaced by R237 Phase 2 as the (b-cheap) candidate keyed column-field-requires-table-backed-parent. The classifier produces a ChildField.ColumnField only on a table-backed parent, but the parent table itself is currently threaded into TypeFetcherGenerator.generateTypeSpec as a parameter rather than carried on the ColumnField record. The switch arm at TypeFetcherGenerator.java:319 reads parentTable from the parameter and throws IllegalStateException if null, treating a structurally-precluded reachability as a defensive guard.

Lift: add a non-null parentTable record component to ColumnField, populated at construction in BuildContext.classifyOutputField (the producer site). The compact constructor takes care of non-null enforcement; the generateTypeSpec parameter and the IllegalStateException arm disappear. The annotation column-field-requires-table-backed-parent retires with R237 regardless of this lift ; the lift adds structural type-system enforcement where R237 already removes the documentation duplication.

Pre-conditions: R237 Phase 1 has shipped (rubrics no longer push the annotation pattern). The lift can proceed independently of R237’s Phase 4 timing.

Out of scope: the multi-record threading on MethodRef.StaticOnly × ReturnTypeRef.TableBoundReturnType (R240’s territory).