Register registers a new valoper. The `addr` parameter is the operator address (stable identity, profile key); `pubKey` is the consensus signing pubkey, from which the signing address is derived.
Auth shape:
- Post-genesis: OriginCaller must equal addr (operator-slot squat guard). Genesis-mode replay (ChainHeight()==0) bypasses, so migration .jsonl txs and historical Register replays succeed.
- Signing-address uniqueness: derived(pubKey) must not already be in signingRegistry, active or retired.
- Front-running guard: post-genesis, derived(pubKey) must not already be an active validator (a fresh registration cannot squat on the consensus address of an existing validator).
Why OriginCaller==addr is sufficient (no IsUserCall): squatting requires the attacker to be able to satisfy OriginCaller==victim, which requires the victim's signing key. r/sys/namereg/v1.Register also gates on IsUserCall, but that's because IT reads unsafe.OriginSend() for the anti-squatting payment and IsUserCall is needed to ensure the OriginSend envelope reflects what landed at this realm rather than a phantom payment from a previous frame. valopers.Register has no per-call payment-receipt check (fees are validated against banker.OriginSend in a way that's symmetric to IsUserCall via direct comparison), so the IsUserCall tightening would only block legitimate `maketx run` flows (operator-authored scripts that legitimately set OriginCaller==operator) without adding identity-squat protection.
Auth-list seeding: the profile's Authorizable owner is set to addr (NOT OriginCaller). At H>0 the squat guard makes them equal anyway; at H==0 the deployer pattern (one signer registers many operators) requires owner == addr so each operator can manage their own profile post-genesis without needing the deployer's auth.
