Group keymap harnesses under development/tests/

Move the four keymap-harness files (test-keymaps.sh/.lua and the Vim
counterparts) into a development/tests/ subfolder so they sit apart from
the interactive dev launchers. REPO_ROOT now climbs two levels, and the
internal source paths, CI invocations, and ONBOARDING tree are updated.

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

development/ONBOARDING.md

@@ -74,11 +74,12 @@ nuwiki/
 │   ├── start-nvim.sh           # Launch Neovim against a scratch wiki
 │   ├── start-vim.sh            # Launch Vim against a scratch wiki
 │   ├── test-personal-wiki.sh   # Launch Vim against your real wiki
-│   ├── test-keymaps.sh         # Neovim keymap harness (CI)
-│   ├── test-keymaps.lua
-│   ├── test-keymaps-vim.sh     # Vim keymap harness (CI)
-│   ├── test-keymaps-vim.vim
-│   └── syntax-diag.vim         # Dump highlighting state for debugging
+│   ├── syntax-diag.vim         # Dump highlighting state for debugging
+│   └── tests/                  # Editor keymap/command harnesses (run in CI)
+│       ├── test-keymaps.sh     # Neovim keymap harness
+│       ├── test-keymaps.lua
+│       ├── test-keymaps-vim.sh # Vim keymap harness
+│       └── test-keymaps-vim.vim
 │
 └── .gitea/
     └── workflows/