Mark fix-mason-installer-deps tasks done, sync specs, archive change

Manual verification (nix flake check, home-manager switch, Mason
reinstall) confirmed on a Nix-capable host. Synced the new
editor-toolchain capability into main specs and archived the change.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BBSd4VBfoKHjE1HR3P8kmn

1 files changed, 43 insertions, 0 deletions

diff --git a/openspec/changes/archive/2026-09-21-fix-mason-installer-deps/specs/editor-toolchain/spec.md b/openspec/changes/archive/2026-09-21-fix-mason-installer-deps/specs/editor-toolchain/spec.md
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+## Purpose
+
+Provisions, via the shared home-manager profile, the runtime toolchain that the
+externally Stow-managed Neovim/mason.nvim config depends on to install and run LSP
+servers, formatters, and debug adapters — without home-manager owning that editor
+config itself.
+
+## ADDED Requirements
+
+### Requirement: mason.nvim installer dependencies are provisioned
+The shared home-manager profile SHALL include a Node.js runtime (providing `npm`), a
+Python 3 interpreter (providing `python3`), and `unzip` on `PATH`, so that
+`mason.nvim`'s package installers can locate the tools they shell out to.
+
+#### Scenario: npm-based Mason package installs successfully
+- **WHEN** the shared home profile is activated and `mason.nvim` installs an
+  npm-based package (for example an LSP server distributed via npm)
+- **THEN** `mason.nvim`'s installer finds `npm` on `PATH` and the installation does
+  not fail with an `ENOENT`/"could not find executable" error for `npm`
+
+#### Scenario: Python-based Mason package installs successfully
+- **WHEN** the shared home profile is activated and `mason.nvim` installs a
+  Python-based package (for example `debugpy`)
+- **THEN** `mason.nvim`'s installer finds a `python3` interpreter on `PATH` and the
+  installation does not fail with a "no python3 installation found" error
+
+#### Scenario: Archive-based Mason package installs successfully
+- **WHEN** the shared home profile is activated and `mason.nvim` installs a package
+  distributed as a zip archive (for example `terraform-ls`)
+- **THEN** `mason.nvim`'s installer finds `unzip` on `PATH` and the installation does
+  not fail with an `ENOENT`/"could not find executable" error for `unzip`
+
+### Requirement: Editor toolchain packages do not manage editor configuration
+Packages provisioned by this capability SHALL supply only the underlying
+interpreters/tools that the externally-managed Neovim dotfiles config depends on;
+this capability SHALL NOT generate, own, or otherwise manage any Neovim
+configuration file (for example `init.lua` or plugin/LSP configuration).
+
+#### Scenario: No competing Neovim configuration is generated
+- **WHEN** the shared home profile provisions the editor toolchain packages
+- **THEN** no Neovim configuration file is created or managed by this capability —
+  the externally Stow-managed dotfiles config remains the sole owner of that
+  configuration