feat: detect ghostty config files by canonical path (#7)

* feat: detect ghostty config files by canonical path

Problem: enabled() only checked for the 'ghostty' filetype, but many
users have ghostty config files detected as 'config' or with no
filetype set. These users got no completions.

Solution: check canonical ghostty config directories
($XDG_CONFIG_HOME/ghostty, ~/.config/ghostty, /etc/ghostty) when the
filetype is 'config' or empty, resolving symlinks to handle indirect
paths.

* fix: revert blanket diagnostics.disable and selene comments

Problem: .luarc.json blanket-disabled four diagnostic categories
project-wide, and selene inline directives were added to suppress
warnings on io.open monkey-patching in tests.

Solution: revert .luarc.json to match main and remove selene comments.

* fix(ci): resolve selene and lua-ls CI failures

Problem: selene flags io.open assignments in test mocks as
incorrect_standard_library_use, and lua-ls reports undefined blink.cmp
types and a need-check-nil on enums_cache. These are pre-existing
issues on main that surface when Lua files change.

Solution: add targeted selene allow comments on the two io.open
mock lines, add minimal blink.cmp type stubs for lua-ls, and
include enums_cache in the nil guard.

spec/ghostty_spec.lua

@@ -57,6 +57,7 @@ local function mock_enums()
     end
     return original_realpath(path)
   end
+  -- selene: allow(incorrect_standard_library_use)
   io.open = function(path, mode)
     if path:match('ghostty%.bash$') then
       return {
@@ -72,6 +73,7 @@ local function mock_enums()
   return function()
     vim.fn.exepath = original_exepath
     vim.uv.fs_realpath = original_realpath
+    -- selene: allow(incorrect_standard_library_use)
     io.open = original_open
   end
 end
@@ -98,6 +100,43 @@ describe('blink-cmp-ghostty', function()
       helpers.delete_buffer(bufnr)
     end)
 
+    it('returns true for config filetype in ghostty config dir', function()
+      local source = require('blink-cmp-ghostty')
+      local bufnr = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_set_option_value('filetype', 'config', { buf = bufnr })
+      local config_path = vim.fn.expand('$HOME/.config/ghostty/config')
+      vim.api.nvim_buf_set_name(bufnr, config_path)
+      local original_realpath = vim.uv.fs_realpath
+      vim.uv.fs_realpath = function(p)
+        if p == config_path then
+          return config_path
+        end
+        return original_realpath(p)
+      end
+      assert.is_true(source.enabled())
+      vim.uv.fs_realpath = original_realpath
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('returns false for config filetype outside ghostty dir', function()
+      local source = require('blink-cmp-ghostty')
+      local bufnr = vim.api.nvim_create_buf(false, true)
+      vim.api.nvim_set_current_buf(bufnr)
+      vim.api.nvim_set_option_value('filetype', 'config', { buf = bufnr })
+      vim.api.nvim_buf_set_name(bufnr, '/tmp/some-other/config')
+      local original_realpath = vim.uv.fs_realpath
+      vim.uv.fs_realpath = function(p)
+        if p == '/tmp/some-other/config' then
+          return '/tmp/some-other/config'
+        end
+        return original_realpath(p)
+      end
+      assert.is_false(source.enabled())
+      vim.uv.fs_realpath = original_realpath
+      helpers.delete_buffer(bufnr)
+    end)
+
     it('returns false for other filetypes', function()
       local bufnr = helpers.create_buffer({}, 'lua')
       local source = require('blink-cmp-ghostty')