docs(gap): log <CR> link-follow new-tab regression

Pressing <CR> on a link now opens a new tab and switches to it instead
of reusing the current window (reported on Vim 9.x + Dein). Records the
investigation so far — the <CR> path is unchanged by recent P1 work and
both client jump paths open same-window by default — and the env gotchas
(stale dein copy, double rtp) to rule out before treating it as a code bug.

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

development/vimwiki-gap.md

@@ -42,6 +42,32 @@ fix site.
   reaches the whole-buffer sweep that `gL<Space>` previously held (the only
   prior entry point). Normal-mode only.
 
+## Regressions (reported by users — verify, then fix)
+
+- [ ] **`<CR>` link-follow opens a new tab instead of reusing the current
+  window** — pressing `<CR>` on a link used to open the target in the *same*
+  tab/window the user was browsing in (upstream behavior). It now opens a
+  **new tab and switches to it**. Reported on Vim 9.x + Dein.
+  _Investigation so far:_ the nuwiki `<CR>` path is **unchanged** by the recent
+  P1 #1/#2/#3 work — `git blame` shows the `<CR>` map (`ftplugin/vimwiki.vim`
+  Vim branch `:206`, Neovim branch `lua/nuwiki/keymaps.lua:161`) and the
+  `follow_link_or_create` → jump-definition chain were not touched; only
+  `<C-S-CR>` was repointed to `follow_link_drop()` in `f65d861`. Both client
+  jump paths open in the current window by default
+  (`vim.lsp.buf.definition()` with no opts; Vim `s:jump_definition()` →
+  `LspDefinition`, `autoload/nuwiki/commands.vim:73`), so the new-tab behavior
+  is **not** coming from nuwiki's own placement logic as written.
+  _Rule out first (env, per memory):_ a **stale dein copy** of the plugin
+  (`bin/nuwiki-ls` + copied ftplugin) and a **double `rtp` entry** where the
+  upstream vimwiki bundle is still loaded alongside nuwiki — either can shadow
+  the `<CR>` map or pull in upstream/`LspDefinition --tab`-style behavior.
+  Recache dein + rebuild + restart LSP and confirm only nuwiki's ftplugin is
+  active before treating this as a nuwiki code bug.
+  _Suspected sites if it reproduces clean:_ vim-lsp's definition-open default
+  (Vim) and the `vim.lsp.buf.definition()` handler (Neovim) — pin which `<CR>`
+  press (bare-word wrap vs. existing-link follow) triggers the tab and whether
+  the server's definition response shape steers placement.
+
 ## P2 — Moderate (real users hit these)
 
 - [ ] **`<Leader>w<Leader>t` collision** — upstream = today-in-new-tab; nuwiki =