feat: replace connection keys with short seed-derived rtun3 keys

Connection keys are now a ~49-char seed (rtun3.) instead of a bundled
~1740-char certificate blob. Both endpoints deterministically derive an
identical Ed25519 CA from the seed and mint ephemeral server/client leaves
at startup (keyderive.rs); the app-layer auth token is derived from the seed.
Target is passed separately on connect (resocks-style).

- connkey.rs: rtun3 seed parse/format
- keyderive.rs: CA/server/client/token derivation
- keygen takes no args; connect requires --target
- remove miniz_oxide; TLS layer unchanged
- add determinism + key-based e2e + wrong-seed-rejected tests
- update wiki, README, design spec, CI smoke

droid-wiki/overview/getting-started.md

@@ -76,26 +76,27 @@ curl --proxy socks5h://127.0.0.1:1180 http://127.0.0.1:4181/
 
 ## Using a connection key
 
-Instead of passing individual certificate paths, you can generate a single connection key:
+Instead of passing individual certificate paths, you can use a short connection key
+from which both ends derive identical credentials:
 
 ```sh
-./target/release/rustunnel keygen --target 127.0.0.1:4180
+./target/release/rustunnel keygen
 ```
 
-Then start the listener with the key (it auto-generates credentials):
+Start the listener with the key:
 
 ```sh
-./target/release/rustunnel listen --connection-key <key>
+./target/release/rustunnel listen --listen 0.0.0.0:4180 --connection-key <key>
 ```
 
-And connect with the same key:
+Connect with the same key, passing the listener address explicitly:
 
 ```sh
-./target/release/rustunnel connect <key>
+./target/release/rustunnel connect --target 127.0.0.1:4180 <key>
 ```
 
 ## Defaults
 
 - Listener bind address: `0.0.0.0:4180`
-- Connector target: required (or taken from connection key)
+- Connector target: required (not stored in the key)
 - Connector SOCKS5 proxy: `127.0.0.1:1180`

droid-wiki/overview/glossary.md

@@ -1,6 +1,6 @@
 # Glossary
 
-**Connection key** — a base64url-encoded, DEFLATE-compressed JSON blob (prefix `rtun2.`) that bundles the CA certificate, server certificate, server key, client certificate, client key, target address, auth token, and version. Generated by `rustunnel keygen` and consumed by `rustunnel listen` and `rustunnel connect`.
+**Connection key** — a short (~49-char) base64url-encoded 32-byte seed (prefix `rtun3.`). Both endpoints derive an identical CA and ephemeral leaf certificates from the seed, so no certificates are ever shipped. Generated by `rustunnel keygen` and consumed by `rustunnel listen` and `rustunnel connect`.
 
 **Connector** — the `rustunnel connect` side. Establishes an outbound HTTPS+mTLS connection to the listener, authenticates, then exposes a local SOCKS5 proxy for local applications.
 

droid-wiki/overview/index.md

@@ -9,7 +9,7 @@ The tool is designed for local labs, development environments, and controlled te
 - **Listener** (`rustunnel listen`) — binds an HTTPS server that accepts mTLS connections from connectors, validates an auth token, then upgrades the connection to a persistent binary-framed tunnel.
 - **Connector** (`rustunnel connect`) — connects to the listener over HTTPS with mTLS, authenticates, then exposes a local SOCKS5 proxy that forwards traffic through the tunnel.
 - **Credential generation** (`rustunnel generate`) — creates a self-signed CA, server certificate, client certificate, and auth token for a local session.
-- **Connection keys** (`rustunnel keygen`) — bundles all credential material into a single compressed base64url string that can be copy-pasted between machines.
+- **Connection keys** (`rustunnel keygen`) — a short ~49-char seed from which both endpoints derive identical TLS material and which can be copy-pasted between machines.
 
 ## Quick links