Resolve all architecture open questions, add 13 ADRs, update specs

Resolved all 11 open questions based on project guidance:

Transport:
- OQ-01/OQ-07: ACME/Let's Encrypt with domain + IP paths (ADR-008)
- OQ-02: Default to n0 relay, --iroh-relay override (ADR-009)
- OQ-05: Transport chaining supported natively (ADR-010)

Client:
- OQ-06: Programmatic-first API, no ~/.ssh/config (ADR-011)

Server:
- OQ-04: Ed25519 + OpenSSH cert-authority, no password auth (ADR-012)
- OQ-08: fail2ban-friendly logging + built-in rate limiting (ADR-013)

TUN:
- OQ-03/OQ-09: Deferred entirely, recommend tun2proxy (ADR-014)
- tun-shim.md marked deprecated

NAPI:
- OQ-10: Expose both connect() and serve() (ADR-016)
- OQ-11: Use napi-rs for FFI bridge (ADR-015)

Additional ADRs created during review:
- ADR-006: No logging of tunnel destinations (was phantom reference)
- ADR-017: Stealth mode protocol multiplexing
- ADR-018: Control channel for pubsub over SSH

Fixed: ADR-002 status → Superseded, ADR-007 title typo,
WRAUTH_SERVER typo, ADR-005 stale wraith-tun refs,
undefined ACL feature removed from server.md,
--proxy semantic difference documented.

docs/architecture/decisions/005-socks5-before-tun.md

@@ -28,11 +28,11 @@ TUN forwards to SOCKS5 rather than directly to SSH because:
 - No root code in the core binary
 
 ## Consequences
-- **Positive**: Core binary is root-free. TUN is optional and separate.
+- **Positive**: Core binary is root-free. TUN functionality is provided by the external `tun2proxy` tool (ADR-014).
 - **Positive**: SOCKS5 is testable without TUN — just `curl` against it.
-- **Positive**: TUN implementation is simplified — it's a thin wrapper around tun2proxy's pattern pointed at localhost:1080.
-- **Negative**: TUN adds one network hop (TUN → localhost SOCKS5 → SSH). The latency impact is negligible (localhost).
-- **Negative**: SOCKS5 doesn't capture UDP (except DNS via SOCKS5h). TUN mode would handle non-DNS UDP via the SOCKS5 UDP association or drop it.
+- **Positive**: The TUN approach is validated by tun2proxy, a well-tested existing tool. No custom TUN code to maintain.
+- **Negative**: VPN-like behavior requires running `tun2proxy` alongside `wraith connect` — two processes instead of one integrated binary.
+- **Negative**: SOCKS5 doesn't capture UDP (except DNS via SOCKS5h). TUN mode via tun2proxy handles this separately.
 
 ## References
 - [client.md](../client.md)