test(config): verify Vim/Neovim config payload parity

Expose the init_options payload builders publicly in both clients
(M.init_options/M.server_settings in Lua, nuwiki#lsp#settings() in Vim) so
they can be inspected. Add editor harnesses that dump each client's
server-bound config as deterministic key=value lines and diff against a
shared golden file: nvim == golden and vim == golden together prove the two
clients send identical config. Add a server-side test asserting the Vim flat
shape and the Neovim {nuwiki:{...}} wrapper desugar to the same WikiConfig.
Wire both harnesses into CI.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lua/nuwiki/lsp.lua

@@ -28,14 +28,16 @@ end
 --- `initializationOptions` payload: the server reads it once at
 --- `initialize` time via `Config::from_init_params`. This is what
 --- delivers `wiki_root`/`wikis`/HTML/diary config to Rust.
-local function init_options()
+--- Public so the config parity harness can inspect the exact payload.
+function M.init_options()
   return resolved_opts()
 end
 
 --- `settings` payload: the same shape, but sent via
 --- `workspace/didChangeConfiguration` after startup. Lets the server
 --- pick up config changes without a restart.
-local function server_settings()
+--- Public so the config parity harness can inspect the exact payload.
+function M.server_settings()
   return { nuwiki = resolved_opts() }
 end
 
@@ -69,8 +71,8 @@ function M.register()
       cmd = command(),
       filetypes = { 'vimwiki' },
       root_markers = { '.git', '.nuwiki' },
-      init_options = init_options(),
-      settings = server_settings(),
+      init_options = M.init_options(),
+      settings = M.server_settings(),
     })
     vim.lsp.enable('nuwiki')
     return
@@ -85,8 +87,8 @@ function M.register()
         name = 'nuwiki',
         cmd = command(),
         root_dir = root_dir_for(ev.file),
-        init_options = init_options(),
-        settings = server_settings(),
+        init_options = M.init_options(),
+        settings = M.server_settings(),
       })
     end,
   })