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+## Why
+
+`mason.nvim` (managed by the externally-owned, Stow-linked Neovim dotfiles config)
+fails to install several LSP/tooling packages on this flake's Home Manager profile:
+`pyright`, `bash-language-server`, `yaml-language-server`,
+`typescript-language-server`, `css-lsp`, and `html-lsp` fail because `npm` is not on
+`PATH`; `debugpy` fails because no `python3`/`python` is on `PATH`; `terraform-ls`
+fails because `unzip` is not on `PATH`. `programs.neovim.withPython3 = true` only
+wires up Neovim's Python *provider* (pynvim) and does not put a `python3` binary on
+`PATH`, so it does not cover this. `js-debug-adapter` and `lua-language-server`
+already install successfully and need no change.
+
+## What Changes
+
+- Provision `nodejs` (for `npm`), `python3`, and `unzip` on `PATH` via the shared
+  Home Manager profile, so `mason.nvim`'s installers can find the interpreters/tools
+  they shell out to.
+
+## Capabilities
+
+### New Capabilities
+- `editor-toolchain`: The shared home-manager profile provisions the runtime
+  toolchain (interpreters, package managers, archive tools) that the externally
+  Stow-managed Neovim/mason.nvim config depends on to install and run LSP servers
+  and debug adapters, without home-manager owning any of that config itself.
+
+### Modified Capabilities
+(none — `developer-environment` covers general most-used CLI tools, not the
+Neovim/mason.nvim dependency contract, so a new capability is used instead of
+overloading that one.)
+
+## Impact
+
+- `modules/home/editor.nix`: extend the existing `home.packages` list (already used
+  for `tree-sitter`/`stdenv.cc`, the same "tools the dotfiles-owned nvim config
+  needs" pattern) with `nodejs`, `python3`, `unzip`.
+- Applies to both Home Manager configs that import this module — `tom@linux` and
+  `tom@darwin` (per `flake.nix`) — covering all supported systems.
+- No changes to the externally-managed dotfiles/Neovim Lua config itself.