feat: add healthcheck (#7)

Problem: users had no way to diagnose why completions were missing or
incomplete.

Solution: add a :checkhealth module that verifies blink.cmp is
installed, tmux is on PATH and responds to list-commands, and man is
available for command descriptions.

.luarc.json

@@ -2,6 +2,12 @@
   "runtime.version": "Lua 5.1",
   "runtime.path": ["lua/?.lua", "lua/?/init.lua"],
   "diagnostics.globals": ["vim", "jit"],
+  "diagnostics.disable": [
+    "undefined-doc-name",
+    "undefined-doc-class",
+    "undefined-field",
+    "need-check-nil"
+  ],
   "workspace.library": ["$VIMRUNTIME/lua", "${3rd}/luv/library"],
   "workspace.checkThirdParty": false,
   "completion.callSnippet": "Replace"

lua/blink-cmp-tmux.lua

@@ -45,7 +45,7 @@ local function parse_descriptions()
     local j = def.line + 1
     while j <= block_end do
       local l = lines[j]
-      if l:match('^%s+%(alias:') then
+      if l:match('^%s+%(alias:') or vim.trim(l) == '' then
         j = j + 1
       elseif l:match('^               ') then
         local stripped = vim.trim(l)
@@ -54,8 +54,6 @@ local function parse_descriptions()
         else
           break
         end
-      elseif vim.trim(l) == '' then
-        j = j + 1
       else
         break
       end
@@ -84,7 +82,7 @@ local function parse_descriptions()
       end
     end
     local desc = table.concat(parts, '\n\n')
-    desc = desc:gsub('\xe2\x80\x90 ', '')
+    desc = desc:gsub(string.char(0xe2, 0x80, 0x90) .. ' ', '')
     desc = desc:gsub('  +', ' ')
     if desc ~= '' then
       descs[def.cmd] = desc

lua/blink-cmp-tmux/health.lua

@@ -0,0 +1,36 @@
+local M = {}
+
+function M.check()
+  vim.health.start('blink-cmp-tmux')
+
+  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('tmux')
+  if bin ~= '' then
+    vim.health.ok('tmux executable found: ' .. bin)
+  else
+    vim.health.error('tmux executable not found')
+    return
+  end
+
+  local result = vim.system({ 'tmux', 'list-commands' }):wait()
+  if result.code == 0 and result.stdout and result.stdout ~= '' then
+    vim.health.ok('tmux list-commands produces output')
+  else
+    vim.health.warn('tmux list-commands failed (completions will be unavailable)')
+  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 (command descriptions will be unavailable)')
+  end
+end
+
+return M