// Package authz is the control-plane-authorization layer: it verifies
// operator-signed destructive ops before the agent executes them. It is what the
// reconcile loop (slice 4) calls to gate destructive desired-state deltas and
// signed one-shot jobs (03 §4, 04). The signing mechanism is proven (Phase 4,
// 14/14) — this package is its production form: a key-type-agnostic SSHSIG
// verifier, the full anti-replay/authorization pipeline, and a durable,
// crash-safe nonce store.
//
// # Mechanism (LOCKED — do not redesign)
//
//   - SSHSIG via golang.org/x/crypto/ssh; no hand-rolled crypto, no raw-Ed25519
//     fallback. pub.Verify dispatches on the key's own algorithm, so the same path
//     accepts ed25519 / sk-ssh-ed25519 (FIDO2) / rsa / ecdsa — a hardware operator
//     key later is a box no-op (Phase 4 §5/§6, doc 04 §7).
//   - Fixed namespace felhom-op-v1 (package constant, never caller-supplied).
//   - The verifier verifies over the RAW received blob bytes and never
//     canonicalizes — the canonical form (sorted-key, whitespace-free JSON) is the
//     signer's contract, shared by the hub and the felhom-sign CLI.
//
// # Pipeline order (load-bearing — Verify)
//
//	parse armor → namespace → parse pubkey → allow-list (by key MATERIAL, not
//	key_id) → crypto verify → parse blob → target → time window → nonce LAST
//
// Each post-crypto stage rejects even with an otherwise-valid signature. The nonce
// is recorded last, so an invalid signature can never consume a nonce. key_id is
// advisory/audit only — authz is the key-material allow-list match.
//
// # Shared-contract dependency (flag for later, not built here)
//
// Signatures only verify if the op-generator (hub) and the felhom-sign CLI produce
// BYTE-IDENTICAL canonical JSON (keys sorted at every level, no insignificant
// whitespace, no trailing newline, UTF-8 — Phase 4 §2). The verifier deliberately
// does NOT re-canonicalize, so a divergence between those two producers surfaces as
// a crypto failure here. A shared canonicalizer that both import would be the right
// home for that contract; it is out of scope for this slice.
package authz