LaTeX throughout. Inline math with `$...$`, display math with `$$...$$`. - Wave mechanics notation (ψ, Ψ, operators with hats) in Parts I–II. - Dirac notation (|ψ⟩, ⟨φ|) formally introduced in Ch 8 and used exclusively from Ch 8 onward, with wave-mechanics equivalents shown in parentheses during the