Initial commit: nvim-agentic-companion plugin

Adds a Claude Code agent and three skills for collaborating with the
user's running Neovim instance via mcp-neovim-server and the official
coder/claudecode.nvim plugin:

- agents/companion.md — the nvim companion identity, prefers runtime
  introspection over training-data guessing
- skills/editor-introspect — read-only queries against the live editor
- skills/editor-act — safe driving (open, jump, toggle, run); no buffer edits
- skills/claude-code-handoff — delegate buffer edits to the in-editor
  Claude Code session so users get a diff to accept or reject

.gitignore

@@ -0,0 +1,3 @@
+.cache/
+.claude/
+*.log