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>

development/tests/test-config.sh

@@ -0,0 +1,52 @@
+#!/usr/bin/env bash
+#
+# development/tests/test-config.sh — verify the Neovim client builds the
+# exact `initialization_options` payload the server expects.
+#
+# Runs development/tests/test-config.lua under headless Neovim, which dumps
+# the server-bound config (wiki_root, file_extension, syntax, log_level,
+# wikis[*]) for a default and a sample scenario as `key=value` lines, then
+# diffs the result against the shared golden config-expected.txt.
+#
+# The Vim harness (test-config-vim.sh) diffs against the SAME golden, so a
+# green run of both proves Vim/Neovim config parity.
+#
+# Exit code: 0 when the payload matches the golden, 1 otherwise.
+
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+TMP="$(mktemp -d -t nuwiki-config-test-XXXXXX)"
+trap 'rm -rf "$TMP"' EXIT
+
+log() { printf '\033[1;34m[config-test]\033[0m %s\n' "$*"; }
+
+GOLDEN="$REPO_ROOT/development/tests/config-expected.txt"
+OUT="$TMP/nvim-config.txt"
+
+# No LSP server needed — we only inspect the payload the client would send.
+INIT="$TMP/init.lua"
+cat > "$INIT" <<EOF
+vim.opt.runtimepath:prepend('$REPO_ROOT')
+EOF
+
+log 'running Neovim config harness…'
+NUWIKI_CONFIG_OUT="$OUT" \
+  timeout 30 nvim --clean -u "$INIT" --headless \
+    -c "luafile $REPO_ROOT/development/tests/test-config.lua" \
+    >"$TMP/nvim.log" 2>&1 || true
+
+if [[ ! -f "$OUT" ]]; then
+  echo 'config harness produced no output' >&2
+  echo '--- nvim log ---' >&2
+  cat "$TMP/nvim.log" >&2 || true
+  exit 1
+fi
+
+if diff -u "$GOLDEN" "$OUT"; then
+  log 'Neovim config payload matches golden ✓'
+  exit 0
+fi
+
+echo 'Neovim config payload DIVERGED from golden (see diff above)' >&2
+exit 1