dev: NUWIKI_DEV_VIMWIKI mode to dogfood the g:vimwiki_* drop-in

The start-vim-coc.sh harness runs `vim --clean`, so it never sources a
user's real vimwiki.vim — meaning g:vimwiki_list is never set and the
g:vimwiki_* drop-in translation was impossible to exercise through the
harness (you'd only ever test the native g:nuwiki_* path).

Add NUWIKI_DEV_VIMWIKI=1: instead of g:nuwiki_*, the generated vimrc
configures an upstream g:vimwiki_list (+ g:vimwiki_toc_header_level etc.)
pointing at the scratch wiki, so nuwiki's client-side translation +
programmatic coc registration run on a real vimwiki-shaped config.

    NUWIKI_DEV_VIMWIKI=1 ./development/start-vim-coc.sh

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

development/start-vim-coc.sh

@@ -24,6 +24,7 @@
 #   NUWIKI_DEV_NO_SEED=1 ./development/start-vim-coc.sh       # use WIKI_DIR as-is (no scratch seeding)
 #   NUWIKI_DEV_SKIP_BUILD=1 ./development/start-vim-coc.sh    # reuse the cached binary
 #   NUWIKI_DEV_COC_JUMP=edit ./development/start-vim-coc.sh   # change coc.preferences.jumpCommand
+#   NUWIKI_DEV_VIMWIKI=1 ./development/start-vim-coc.sh       # drive nuwiki from a g:vimwiki_list config (drop-in)
 #
 # The release binary is rebuilt on every launch so source changes always reach
 # the running LSP. `cargo build --release` is incremental, so this is a fast
@@ -86,6 +87,29 @@ EOF
 
 write_vimrc() {
   mkdir -p "$DEV_DIR"
+
+  # Wiki config block. Default: native g:nuwiki_* (single wiki). With
+  # NUWIKI_DEV_VIMWIKI=1: an upstream g:vimwiki_list config instead, to dogfood
+  # the g:vimwiki_* drop-in translation (the path real vimwiki migrants use).
+  local WIKI_CFG
+  if [[ "${NUWIKI_DEV_VIMWIKI:-0}" == "1" ]]; then
+    log "NUWIKI_DEV_VIMWIKI=1 — driving nuwiki from an upstream g:vimwiki_list config"
+    WIKI_CFG="\" Upstream vimwiki config (drop-in). nuwiki translates these.
+let g:vimwiki_toc_header_level = 2
+let g:vimwiki_html_header_numbering = 2
+let g:vimwiki_html_header_numbering_sym = ' -'
+let g:vimwiki_list = [{'path': '${WIKI_DIR}', 'path_html': '${DEV_DIR}/html', 'ext': '.wiki'}]"
+  else
+    WIKI_CFG="let g:nuwiki_wiki_root    = '${WIKI_DIR}'
+let g:nuwiki_file_extension = '.wiki'
+let g:nuwiki_diary_rel_path = 'diary'
+\" Display settings exercise the global shorthand: :NuwikiTOC writes
+\" \`== Contents ==\` (level 2) and HTML export numbers headings.
+let g:nuwiki_toc_header_level = 2
+let g:nuwiki_html_header_numbering = 2
+let g:nuwiki_html_header_numbering_sym = ' -'"
+  fi
+
   cat > "$VIMRC" <<EOF
 " start-vim-coc.sh: generated minimal config for nuwiki development (coc.nvim).
 " Regenerated on every launch; edit start-vim-coc.sh, not this file.
@@ -109,17 +133,11 @@ let g:coc_config_home = '${DEV_DIR}'
 let g:coc_data_home   = '${COC_DATA}'
 
 let g:nuwiki_binary_path  = '${REPO_ROOT}/bin/nuwiki-ls'
-let g:nuwiki_wiki_root    = '${WIKI_DIR}'
-let g:nuwiki_file_extension = '.wiki'
 let g:nuwiki_syntax       = 'vimwiki'
-let g:nuwiki_diary_rel_path = 'diary'
 let g:nuwiki_log_level    = 'info'
 " nuwiki auto-registers itself with coc from these globals (no coc-settings.json
-" languageserver block). Display settings exercise the global shorthand:
-" :NuwikiTOC writes `== Contents ==` (level 2) and HTML export numbers headings.
-let g:nuwiki_toc_header_level = 2
-let g:nuwiki_html_header_numbering = 2
-let g:nuwiki_html_header_numbering_sym = ' -'
+" languageserver block).
+${WIKI_CFG}
 
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