Replace test-personal-wiki.sh with a generated sample wiki

Drop the personal-wiki launcher in favor of a self-contained fixture
the dev launchers seed into the cache. write_sample_wiki() lays down
one page per vimwiki feature group (syntax, lists, tables, links,
notes, diary) so every plugin feature has something to exercise
without touching a real wiki.

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

development/ONBOARDING.md

@@ -71,9 +71,8 @@ nuwiki/
 ├── development/                # Developer-only tooling and docs (not shipped)
 │   ├── ONBOARDING.md           # This file
 │   ├── nuwiki-architecture.html
-│   ├── 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
+│   ├── start-nvim.sh           # Launch Neovim against a generated sample wiki
+│   ├── start-vim.sh            # Launch Vim against a generated sample wiki
 │   ├── syntax-diag.vim         # Dump highlighting state for debugging
 │   └── tests/                  # Editor keymap/command harnesses (run in CI)
 │       ├── test-keymaps.sh     # Neovim keymap harness