feat: initial blink-cmp-ssh implementation

Problem: the existing blink-cmp-sshconfig plugin uses a synchronous,
build-time Python scraping approach that requires uv and make to
generate a static Lua file.

Solution: implement a runtime, async blink.cmp source that parses
ssh_config keywords from man ssh_config and enum values from ssh -Q
queries, matching the architecture of blink-cmp-tmux and
blink-cmp-ghostty.

README.md

@@ -0,0 +1,49 @@
+# blink-cmp-ssh
+
+SSH configuration completion source for
+[blink.cmp](https://github.com/saghen/blink.cmp).
+
+## Features
+
+- Completes `ssh_config` keywords with man page documentation
+- Provides enum values for keywords with known option sets (ciphers,
+  MACs, key exchange algorithms, etc.)
+- Keyword and enum data fetched asynchronously at runtime via
+  `man ssh_config` and `ssh -Q`
+
+## Requirements
+
+- Neovim 0.10.0+
+- [blink.cmp](https://github.com/saghen/blink.cmp)
+- `ssh` and `man` executables
+
+## Installation
+
+Install via
+[luarocks](https://luarocks.org/modules/barrettruth/blink-cmp-ssh):
+
+```
+luarocks install blink-cmp-ssh
+```
+
+Or with lazy.nvim:
+
+```lua
+{
+  'saghen/blink.cmp',
+  dependencies = {
+    'barrettruth/blink-cmp-ssh',
+  },
+  opts = {
+    sources = {
+      default = { 'ssh' },
+      providers = {
+        ssh = {
+          name = 'SSH',
+          module = 'blink-cmp-ssh',
+        },
+      },
+    },
+  },
+}
+```