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.

.luarc.json

@@ -0,0 +1,8 @@
+{
+  "runtime.version": "Lua 5.1",
+  "runtime.path": ["lua/?.lua", "lua/?/init.lua"],
+  "diagnostics.globals": ["vim", "jit"],
+  "workspace.library": ["$VIMRUNTIME/lua", "${3rd}/luv/library"],
+  "workspace.checkThirdParty": false,
+  "completion.callSnippet": "Replace"
+}