2025-08-14 updates

[daler]

vim

• Replace vim-sleuth with indent-o-matic for better indentation detection
• Replace nvim-cmp with blink.cmp for autocompletion (about the same features but with simplified config)
• Update checkbox rendering in markdown files
• Add zenfade colorscheme (not enabled by default)
• Nicer diff deletion symbol
• Add lush plugin
• Add treesj plugin
• Bump installed nvim version to 0.10.4

setup

• conda installation dir can be configured via env var CONDA_INSTALLATION_DIR
• dockerfile uses conda rather than mamba for testing

docs

Nvim documentation overhaul. This now includes a new sphinx extension which
inspects the git history to create a changelog of a plugin. This looks for the
plugin name in filenames, commit messages, and changed text in an attempt to be
more transparent about changes over time.

The updates also include splitting the vim plugins from the main vim docs and
rewriting some supporting docs for vim.