Bundle accumulated plugin work that had been sitting in the working
tree: add CodeCompanion, golf, neotest (with rustaceanvim adapter),
nvim-bacon, vim-pencil, and quickscope; bump rustaceanvim to ^6 with
clippy/rustfmt settings and a neotest dependency; add an Obsidian
checkbox order; rework trouble keymaps to free <leader>xx and add a
sidebar diagnostic toggle. Drop cyberdream — tokyonight is the
current colorscheme.