fix(conflict): resolve LuaLS duplicate-doc-field and inject-field errors

Problem: lua-language-server reports duplicate @class definitions for
ConflictKeymaps and ConflictConfig (defined in both init.lua and
conflict.lua), and inject-field errors for the untyped parser table.

Solution: remove duplicate @class annotations from conflict.lua
(init.lua is the canonical source), and annotate the parser's current
variable as diffs.ConflictRegion? so LuaLS knows its shape.

lua/diffs/conflict.lua

@@ -1,17 +1,3 @@
----@class diffs.ConflictKeymaps
----@field ours string|false
----@field theirs string|false
----@field both string|false
----@field none string|false
----@field next string|false
----@field prev string|false
-
----@class diffs.ConflictConfig
----@field enabled boolean
----@field disable_diagnostics boolean
----@field show_virtual_text boolean
----@field keymaps diffs.ConflictKeymaps
-
 ---@class diffs.ConflictRegion
 ---@field marker_ours integer
 ---@field ours_start integer
@@ -41,6 +27,7 @@ local PRIORITY_LINE_BG = 200
 function M.parse(lines)
   local regions = {}
   local state = 'idle'
+  ---@type diffs.ConflictRegion?
   local current = nil
 
   for i, line in ipairs(lines) do