The hard part of PQC migration is not knowing that RSA and elliptic-curve cryptography are exposed to future quantum computers. The hard part is finding where those algorithms sit across products, suppliers, customer paths and signing systems.
A CTO needs a migration programme that survives budget cycles: visible evidence, a maintained inventory, supplier commitments, pilot results and governance rules that stop new systems from adding fresh migration debt.
The external website scan is the fastest first signal. The inventory is the control point. Supplier evidence and pilots turn the inventory into a roadmap.