theorem instability_from_trace {a_ρρ a_TT a_JJ : ℝ}
(htrace : 0 < jacobian3DTrace a_ρρ a_TT a_JJ) :
0 < a_ρρ + a_TT + a_JJ := by
simp only [jacobian3DTrace] at htrace; exact htrace## Entry-Exit Core Definitions (merged from EntryExitDefs.lean)