docs: web client variant architecture — Pure JS, Hybrid, Full WASM
WEB_VARIANTS.md with Mermaid diagrams for all three variants:
- Comparison table (bundle, transport, encryption, FEC, latency)
- Per-variant architecture diagrams + sequence flows
- WASM module structure (FEC + crypto exports)
- FEC wire format (3-byte header + 256-byte padded symbols)
- Encryption flow (X25519 DH → HKDF → ChaCha20-Poly1305)
- Nonce construction (matches native wzp-crypto)
- Send/receive pipeline details for Full variant
- Shared infrastructure (wzp-core.js, AudioWorklet, boot sequence)
- Deployment guides (Caddy, direct TLS, URL patterns)
- Browser console test commands for FEC and crypto
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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