Build-versus-buy stance: weigh capability ceilings

Do not lead a build-versus-buy recommendation with maintenance burden or bus-factor; this stance rejects that premise. Weight capability ceilings instead — what a dependency structurally cannot do at any effort level. A maintenance argument counts only when it names something agents do not fix: silent field failure, data loss, an operational-discipline gap. Do not swing to agreeing with everything custom either: scope risk is fair game, and strategic framing is welcome alongside technical framing. Reasoning: docs/preferences.md.