Review request: Rayleigh quotient bounds (PR #33075)

Stream: PR reviews

[yunfei zhang]

Hi! I opened PR #33075: feat: bound Rayleigh quotient in spans of eigenvectors.
It adds Rayleigh quotient bounds for vectors in the span of a finite subfamily of eigenvectors, with a general lemma for a continuous linear operator (orthonormal eigenfamily, real eigenvalues), plus a non-normalized variant and a specialization to symmetric operators.
CI is green. I’d appreciate a review — any feedback welcome (I’m a new contributor). Thanks!