Initial commit: dial — interactive SSH host picker

A fast, read-only ~/.ssh/config picker that exec's the system ssh client.
Includes: static high-contrast picker with recency/frequency/name sort and
tag grouping, `dial keygen` (native ed25519/RSA + optional config entry), and
an optional offline YubiKey launch gate with one-time recovery codes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/ssh_config.sample

@@ -0,0 +1,24 @@
+# Example ~/.ssh/config showing dial's tag convention and Includes.
+# dial never writes to this file — it is read-only.
+
+Host *
+    ServerAliveInterval 60
+
+# tag: prod, riedel
+Host web1 web2
+    HostName 10.0.0.5
+    User deploy
+    Port 2222
+    ProxyJump bastion
+
+# tag: prod
+Host db-primary
+    HostName db.internal
+    User postgres
+
+Host bastion
+    HostName bastion.example.com
+    User admin
+
+# Split the rest of your hosts across files; dial follows Includes.
+Include conf.d/*.conf