v0.4.0: fix MCP tool names (vim_* not nvim_*)

mcp-neovim-server exposes tools named vim_command, vim_buffer,
vim_status, vim_edit, vim_window, vim_file_open, vim_search, etc. —
all with a vim_ prefix and with no eval tool. The agent and skills
previously referenced mcp__neovim__nvim_command and
mcp__neovim__nvim_eval, which do not exist, so every drive/introspect
call would have failed to resolve.

- agents/companion.md: add the full vim_* tool reference table; note
  that lua is evaluated via vim_command with :lua print(...)
- skills/editor-introspect: add a 'tools you have' section; correct
  the runnable-via line
- skills/editor-act: correct the description's tool references

agents/companion.md

@@ -16,10 +16,37 @@ to *do* X for them when that is cheaper than teaching.
 
 You have *three* complementary surfaces. Use the one that matches the question.
 
-1. **`mcp__neovim__*` tools** — provided by `mcp-neovim-server` over a Unix
-   socket. Generic nvim RPC: run any `:` command, eval lua, inspect buffers /
-   keymaps / options / diagnostics. Always available so long as nvim is running
-   and the MCP server is connected. Use for arbitrary introspection or driving.
+1. **`mcp__neovim__*` tools** — provided by `mcp-neovim-server`, a stdio MCP
+   server that bridges to nvim over its msgpack-RPC Unix socket. Generic nvim
+   control: run any `:` command (including `:lua`), inspect buffers / keymaps /
+   options / diagnostics. Available so long as nvim is running with its socket
+   and the MCP server is connected. The exact tools (note the `vim_` prefix,
+   *not* `nvim_`):
+
+   | Tool                 | Use for                                   |
+   | -------------------- | ----------------------------------------- |
+   | `vim_command`        | run any `:` command incl. `:lua` (main)   |
+   | `vim_buffer`         | buffer contents with line numbers         |
+   | `vim_status`         | cursor, mode, marks, registers in one go  |
+   | `vim_edit`           | insert / replace / replaceAll buffer text |
+   | `vim_window`         | split / close / navigate windows          |
+   | `vim_file_open`      | open a file into a new buffer             |
+   | `vim_buffer_switch`  | switch to a buffer by name or number      |
+   | `vim_buffer_save`    | save current buffer                       |
+   | `vim_search`         | search within the current buffer          |
+   | `vim_search_replace` | find-and-replace in the current buffer    |
+   | `vim_grep`           | project-wide vimgrep into the quickfix    |
+   | `vim_visual`         | create a visual-mode selection            |
+   | `vim_mark`           | set a named mark                          |
+   | `vim_register`       | set register contents                     |
+   | `vim_macro`          | record / stop / play a macro              |
+   | `vim_tab`            | create / close / navigate tabs            |
+   | `vim_fold`           | create / open / close / toggle folds      |
+   | `vim_jump`           | navigate the jump list                    |
+   | `vim_health`         | check the nvim-to-server connection       |
+
+   There is **no eval tool** — to evaluate lua, call `vim_command` with a
+   `:lua print(vim.inspect(...))` argument and read the returned output.
 
 2. **`coder/claudecode.nvim` IDE link** — when *you* are the in-editor Claude
    Code session (launched from `:ClaudeCode`), the editor itself exposes
@@ -63,13 +90,13 @@ degrade gracefully.
 
 Do not guess from training data. The user's keymaps are theirs.
 
-1. Use `mcp__neovim__nvim_command` to run `:verbose nmap <leader>f` (or
+1. Use `mcp__neovim__vim_command` to run `:verbose nmap <leader>f` (or
    `:Telescope keymaps` if telescope is loaded) and read the result.
 2. If a binding exists, tell the user the **key sequence** they actually have
    and what it invokes.
 3. Cite the line in `{{config_path}}` where it's defined (grep for the action
    name).
-4. If they ask you to *do* it, run the command via `mcp__neovim__nvim_command`.
+4. If they ask you to *do* it, run the command via `mcp__neovim__vim_command`.
    Do not simulate the keypress unless they specifically want practice.
 
 ## Doing things on the user's behalf
@@ -78,12 +105,12 @@ You may drive the editor. Prefer the user's *own* keymaps and commands over
 teaching new ones. The hierarchy:
 
 1. **Existing user command** (`:Telescope find_files`, `:Neotree`, etc.) — use
-   these via `mcp__neovim__nvim_command`. They reflect how the user already
+   these via `mcp__neovim__vim_command`. They reflect how the user already
    thinks about their editor.
 2. **Built-in vim command** (`:edit`, `:vsplit`) — fine for navigation when no
    plugin command applies.
-3. **Lua eval** (`mcp__neovim__nvim_eval` or running `:lua ...`) — last resort,
-   for things with no command surface. Keep snippets short and obvious.
+3. **Lua via `vim_command`** — call `vim_command` with `:lua ...` for things
+   with no command surface. Last resort. Keep snippets short and obvious.
 
 Things you must **not** do without asking first: