docs: add scope headers + Next: footers to all tour docs

Each of the eight tour docs (README, DESIGN, docs/CRYPTO,
docs/FORMATS, docs/SECURITY, crates/relicario-core/ARCHITECTURE,
crates/relicario-cli/ARCHITECTURE, extension/ARCHITECTURE) now
declares its scope in a blockquote under its H1 and ends with a
single-line "Next:" pointer to the next doc in the canonical
reading order: README → DESIGN → CRYPTO → FORMATS → SECURITY →
core → cli → extension.

Also trimmed README's mid-section "Architecture" stub to a one-
paragraph pointer at DESIGN.md (was duplicating cross-codebase
content and referencing a non-existent docs/architecture/ tree).

Renamed docs/CRYPTO.md's H1 from "Relicario — Architecture" to
"Relicario — Crypto Pipeline" to match the file's renamed scope.

Spec: docs/superpowers/specs/2026-05-30-doc-structure-redesign-design.md

README.md

@@ -4,6 +4,8 @@
 
 # Relicario
 
+> **Audience:** users + evaluators. This doc owns the pitch, security-model summary, quick-start commands, reference-image explanation, recovery-QR overview, and roadmap teaser. Goes no deeper — for the system tour see [DESIGN.md](DESIGN.md), for crypto see [docs/CRYPTO.md](docs/CRYPTO.md).
+
 A git-backed, self-hostable password manager where decryption requires two independent factors: a passphrase you memorize and a reference JPEG that carries a hidden secret. Compromise of either factor alone is insufficient.
 
 The server only ever sees opaque ciphertext. There is nothing else going on. This README is the security proof.
@@ -135,34 +137,9 @@ Recommended practice: print the QR, store it offline (safe, deposit box), and fo
 
 ## Architecture
 
-```
-relicario/
-├── crates/
-│   ├── relicario-core/     # Platform-agnostic library (no filesystem, no network)
-│   │   ├── crypto.rs    # Argon2id KDF + XChaCha20-Poly1305 AEAD
-│   │   ├── imgsecret.rs # DCT steganography: embed/extract 256-bit secrets in JPEGs
-│   │   ├── item.rs      # Item, Field, Manifest data model (serde)
-│   │   ├── item_types/  # Per-type cores (Login, SecureNote, Card, Identity, Key, Document, Totp)
-│   │   ├── attachment.rs # Encrypted attachment helpers (content-addressed)
-│   │   ├── settings.rs  # VaultSettings (retention, generator defaults, caps)
-│   │   ├── backup.rs    # `.relbak` encrypted-backup envelope
-│   │   ├── device.rs    # ed25519 device keys + revocation entries
-│   │   ├── recovery_qr.rs # Paper-printable image_secret backup (XChaCha20-Poly1305 + Argon2id)
-│   │   ├── import_lastpass.rs # LastPass CSV → typed items
-│   │   └── vault.rs     # Encrypt/decrypt items, manifest, settings
-│   ├── relicario-cli/      # CLI binary: filesystem, git, terminal I/O
-│   ├── relicario-wasm/     # Thin wasm-bindgen wrapper for the browser extension
-│   └── relicario-server/   # Pre-receive hook: device-signature verification
-├── extension/              # Chrome MV3 / Firefox WebExtension (TypeScript)
-└── docs/
-    ├── ARCHITECTURE.md    # System overview + flow diagrams
-    ├── SECURITY.md        # Manifest integrity model + threat notes
-    ├── architecture/      # Cross-codebase + per-codebase architecture docs
-    └── superpowers/
-        └── specs/         # Design specifications with full threat model
-```
+A short tour of the four codebases and how they fit together lives in [DESIGN.md](DESIGN.md). Crypto pipeline diagrams are in [docs/CRYPTO.md](docs/CRYPTO.md); the wire format reference is [docs/FORMATS.md](docs/FORMATS.md); the threat model is [docs/SECURITY.md](docs/SECURITY.md).
 
-`relicario-core` takes bytes and returns bytes. It has no knowledge of filesystems, git, or networks. This makes it portable to WASM (browser extension), Android (JNI), and iOS (Swift bridge).
+`relicario-core` is the platform-agnostic bytes-in/bytes-out heart — no filesystem, no network. The CLI binary and the browser-extension WASM bridge both consume it. See per-codebase deep-dives in `crates/*/ARCHITECTURE.md` and `extension/ARCHITECTURE.md`.
 
 ### Crypto primitives
 
@@ -248,3 +225,7 @@ GPL-3.0-or-later — see [LICENSE](LICENSE).
 ---
 
 Built by [Aaron D. Lee](https://adlee.work). Design spec and threat model in `docs/superpowers/specs/`.
+
+---
+
+**Next:** [DESIGN.md](DESIGN.md) — the system tour.