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.

lua/blink-cmp-ssh/health.lua

@@ -0,0 +1,36 @@
+local M = {}
+
+function M.check()
+  vim.health.start('blink-cmp-ssh')
+
+  local ok = pcall(require, 'blink.cmp')
+  if ok then
+    vim.health.ok('blink.cmp is installed')
+  else
+    vim.health.error('blink.cmp is not installed')
+  end
+
+  local bin = vim.fn.exepath('ssh')
+  if bin ~= '' then
+    vim.health.ok('ssh executable found: ' .. bin)
+  else
+    vim.health.error('ssh executable not found')
+    return
+  end
+
+  local man_bin = vim.fn.exepath('man')
+  if man_bin ~= '' then
+    vim.health.ok('man executable found: ' .. man_bin)
+  else
+    vim.health.warn('man executable not found (keyword descriptions will be unavailable)')
+  end
+
+  local result = vim.system({ 'ssh', '-Q', 'cipher' }):wait()
+  if result.code == 0 and result.stdout and result.stdout ~= '' then
+    vim.health.ok('ssh -Q cipher produces output')
+  else
+    vim.health.warn('ssh -Q cipher failed (enum completions will be unavailable)')
+  end
+end
+
+return M

lua/blink-cmp-ssh/types.lua

@@ -0,0 +1,16 @@
+---@class blink.cmp.Source
+
+---@class blink.cmp.CompletionItem
+---@field label string
+---@field kind? integer
+---@field documentation? {kind: string, value: string}
+---@field filterText? string
+
+---@class blink.cmp.Context
+---@field line string
+---@field cursor integer[]
+
+---@class blink.cmp.CompletionResponse
+---@field is_incomplete_forward? boolean
+---@field is_incomplete_backward? boolean
+---@field items blink.cmp.CompletionItem[]