Post-R438 stale-reference residue: ConditionResolution javadoc + fkjoin-alias-dead-storage item

BuildContext.ConditionResolution javadoc drift. The record’s javadoc still asserts "exactly one of ref and error is non-null," but resolveConditionRef returns (null, null) in two cases: when className / methodName / svc is absent, and when reflectTableMethod fails. That both-null case is exactly what R438’s review-fix (b0ab513) added caller guards for (res.ref() == null checks in the three parsePathElement branches). Correct the javadoc to state that a (null, null) result means "unresolved" and that callers must guard res.ref() == null in addition to res.error() != null.

fkjoin-alias-dead-storage Backlog item is stale. roadmap/fkjoin-alias-dead-storage.md references the deleted types FkJoin.alias / ConditionJoin.alias and a stale BuildContext.java:694 line number; R438’s reshape moved that concern onto Hop.alias. Refresh the item’s prose against Hop.alias (the dead-storage question survives the reshape, just under a new component) or retire it if the alias is now consumed.