Decouple file-explorer from shell + nvim layers; remove orphaned NERDTree config

[lukoshkin]

Summary

The NERDTree → nvim-tree migration left the file-explorer coupled across two
layers and two plugins, and left the old NERDTree config orphaned but still
sourced. Switching to another explorer later (neo-tree, oil.nvim, mini.files,
…) currently means editing the shell layer and the Avante integration,
not just the explorer's own spec. This issue tracks decoupling the explorer so
a future switch is a config-only change, plus deleting the dead NERDTree
config.

Context: v <dir> regressed to opening a blank buffer (netrw disabled +
nvim-tree lazy-loaded on keys, so nothing hijacks the directory at startup).
A stopgap fix was added to the shell v() that hardcodes
require('nvim-tree.api').tree.open() — which is itself an example of the
coupling this issue wants to remove.

Steps to reproduce

The coupling is structural, not a runtime crash. To see the blast radius of a
switch:

1. grep -rIn -e 'nvim-tree' -e 'NvimTree' conf/ (excluding nvim-web-devicons
   and nvim-treesitter, which are unrelated).
2. Observe explorer-specific references in the shell (aliases-functions.sh)
   and in Avante (ai/avante.lua), not just in the explorer's own spec.

Expected: the explorer plugin is self-contained — switching it touches only
its own spec file (plus, at most, one filetype-name constant).
Actual: a switch touches 4 files across 3 concerns (explorer spec, shell,
AI integration, treesitter filetype guard), and two explorers' configs are
present at once (nvim-tree live in edge/, NERDTree orphaned in legacy
init.vim).

Grounding

Verified facts (read from the code)

Hard coupling — must rewrite on a switch:

• conf/nvim/edge/lua/user/core/nvim-tree.lua:46,62,12,54,57,81,89 — the
  explorer itself: plugin spec, require("nvim-tree").setup{}, on_attach
  keymaps via require("nvim-tree.api"), the NvimTree-User augroup, and a
  QuitPre autocmd that matches the NvimTree_<tab> buffer name to
  auto-close the last window. Unavoidably explorer-specific.
• conf/bash/aliases-functions.sh:122 — v() runs
  vim -c "lua require('nvim-tree.api').tree.open()" on a directory arg. The
  only nvim-tree leak into the shell layer.
• conf/nvim/edge/lua/user/ai/avante.lua:49,52-53,58,61-62,92 — Avante
  integration: require "avante.extensions.nvim_tree", two keymaps gated on
  ft = "NvimTree", and selector.exclude_auto_select = { "NvimTree" }.
  This is the easy-to-miss one — Avante ships a dedicated nvim-tree
  extension for selecting files into AI context; a target explorer may not
  have an equivalent.

Soft coupling — one-line edits, harmless if left stale:

• conf/nvim/edge/lua/user/core/treesitter.lua:30-31 —
  highlight_disable = { NvimTree = true, latex = true } disables TS
  highlighting on the NvimTree filetype. Update the filetype name on switch.

Orphaned legacy (NERDTree, dead weight):

• conf/nvim/init.vim:10 — still sources conf/nvim/conf/nerdtree.vim.
• conf/nvim/conf/nerdtree.vim:1,3-4,6-17 — full NERDTree config: Plug 'preservim/nerdtree', <leader>nt/<leader>nf maps, VimEnter
  open-on-directory autocmd, and the close-if-last-window autocmd. Belongs to
  the legacy init.vim path, parallel to the live edge/ Lua config.

Not coupling (false positives, leave alone):

• nvim-tree/nvim-web-devicons in bufferline.lua:4, lualine.lua:79,
  telescope.lua:18, avante.lua:266, nvim-tree.lua:52 — that's the
  icons library (GitHub org is nvim-tree), not the explorer.
• All nvim-treesitter* references — different plugin.

Hypothesis (needs confirmation)

• The cleanest decoupling for the shell layer is to make v() generic
  (vim "$@") and let Neovim own directory-opening via netrw-hijack — every
  major explorer (nvim-tree, neo-tree, oil) supports it; mini.files needs a
  small autocmd. Confirm by: re-enabling netrw hijack + ensuring the explorer
  loads on a directory, then nvim <dir> opens the tree with no shell logic.
• The Avante coupling cannot be fully removed (it's an inherent
  integration), but it can be isolated to one block so a switch is a single
  localized edit.

Key files

Path	Role
conf/nvim/edge/lua/user/core/nvim-tree.lua	The explorer spec + setup + keymaps + auto-close autocmd (hard coupling).
conf/bash/aliases-functions.sh:117-129	v() — shell entry point; hardcodes the nvim-tree API on a directory arg (stopgap to decouple).
conf/nvim/edge/lua/user/ai/avante.lua:49-92	Avante ↔ nvim-tree integration (hard coupling; easy to miss).
conf/nvim/edge/lua/user/core/treesitter.lua:30-31	highlight_disable keyed on the NvimTree filetype (soft coupling).
conf/nvim/init.vim:10	Sources the orphaned NERDTree config (legacy path).
conf/nvim/conf/nerdtree.vim	Dead NERDTree config to delete.

Run / test commands

• Audit coupling: grep -rIn -e 'nvim-tree' -e 'NvimTree' conf/ | grep -ivE 'web-devicons|treesitter'
• Manual check: v ~/some/dir and nvim ~/some/dir → explorer opens rooted at the dir.
• After legacy removal: nvim starts clean with no missing-source error.

Acceptance criteria

• Switching the explorer plugin requires editing only its own spec file
  (core/<explorer>.lua) plus at most the one treesitter filetype constant —
  no shell edit required.
• v <dir> and bare nvim <dir> both open the configured explorer rooted
  at the directory, with no nvim-tree plugin name hardcoded in
  conf/bash/aliases-functions.sh.
• The Avante ↔ explorer integration is isolated to a single, clearly
  marked block in ai/avante.lua (one place to edit on a switch).
• conf/nvim/conf/nerdtree.vim is removed and conf/nvim/init.vim no
  longer sources it; launching nvim via the legacy path produces no error.
• grep -rIn -e 'nvim-tree' -e 'NvimTree' conf/ | grep -ivE 'web-devicons|treesitter'
  returns only the explorer spec file and the (clearly-scoped) Avante block.

Fix directions

• Shell layer: revert v() to generic vim "$@"; move directory-opening
  into Neovim via the explorer's netrw-hijack (re-enable hijack + load the
  explorer on a directory). Keeps the shell explorer-agnostic forever.
• Alternative (lighter): keep v() handling dirs but read the open command
  from a single variable (e.g. V_TREE_CMD), so a switch is one shell line.
• Avante: wrap the nvim-tree extension wiring in one local block /
  helper so a switch is a single localized edit (or guard with pcall so a
  missing extension degrades gracefully).
• Legacy: delete conf/nvim/conf/nerdtree.vim and drop the source line
  in conf/nvim/init.vim (verify the legacy init.vim path is still wanted at
  all; if not, that's a larger separate cleanup).

References

• No sibling issues (first issue on this topic).
• Originating discussion: v <dir> blank-buffer regression and the stopgap
  fix in conf/bash/aliases-functions.sh.

Resolution

Reference this issue in the fix commit(s). The repo's git log uses
imperative, capitalized subjects (e.g. "Add macOS keyboard and shell
support") — match that and mention #<NNN> in the body. After merge, close
#<NNN> with a comment naming the resolving commit(s). Full protocol: see the
issue-fix skill.