Add basic auto-completion to Neovim and comprehensive documentation

- Add nvim-cmp plugin with buffer and path completion sources
- Configure intuitive keybindings for completion navigation:
  * Ctrl+Space to trigger completion manually
  * Tab/Shift+Tab for menu navigation
  * Enter to accept completion, Ctrl+e to close menu
- Enable autoEnableSources for automatic plugin management

- Add comprehensive "Code Editing & Auto-completion" section to README:
  * Document all key features: Gruvbox theme, Tree-sitter, file explorer
  * Provide complete auto-completion usage guide with keybindings
  * Include essential keybinding reference for file operations, clipboard, git
  * Explain completion sources: buffer words and file path suggestions

Benefits:
- Simple, non-intrusive auto-completion without language servers
- Word completion from open buffers for faster typing
- Path completion for file navigation and imports
- Clear documentation for all Neovim features and keybindings
- Follows standard completion UI patterns users expect

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

README.md

@@ -297,6 +297,63 @@ Launch with `lazygit` in any git repository for:
 - File tree navigation with git status
 - Intuitive keyboard shortcuts and help system
 
+### 🌟 Code Editing & Auto-completion
+
+**Tool**: Neovim with NixVim
+**Purpose**: Modern text editor with declarative configuration and basic auto-completion
+
+Configured with essential plugins and basic auto-completion for improved productivity:
+
+#### Key Features:
+- **Gruvbox theme**: Dark theme with hard contrast for better readability
+- **Tree-sitter**: Advanced syntax highlighting for multiple languages
+- **File explorer**: nvim-tree for project navigation
+- **Auto-completion**: Basic word and path completion without language servers
+- **Git integration**: vim-fugitive for version control operations
+- **Markdown rendering**: Live preview for documentation
+
+#### Auto-completion Usage:
+
+**Basic completion:**
+```
+Ctrl+Space    # Trigger completion menu manually
+Tab           # Navigate to next completion item
+Shift+Tab     # Navigate to previous completion item
+Enter         # Accept selected completion
+Ctrl+e        # Close completion menu
+```
+
+**Completion sources:**
+- **Buffer completion**: Suggests words from currently open files
+- **Path completion**: Suggests file and directory paths when typing paths
+
+#### Essential Keybindings:
+
+**File operations:**
+```
+<leader>e     # Toggle file explorer (nvim-tree)
+<leader>w     # Save current file
+<leader>q     # Quit current buffer
+<leader>o     # Open file with system default app
+<leader>f     # Show current file in Finder
+```
+
+**System clipboard:**
+```
+<leader>y     # Copy selection to system clipboard
+<leader>p     # Paste from system clipboard
+```
+
+**Git operations:**
+```
+<leader>gs    # Git status
+<leader>gd    # Git diff
+<leader>gc    # Git commit
+<leader>gp    # Git push
+```
+
+**Note**: Leader key is set to spacebar. Basic auto-completion provides word suggestions from open files and path completion without requiring language server setup.
+
 ### 🌟 File Synchronization & Backup
 
 **Tool**: rsync

modules/nvim.nix

@@ -86,6 +86,27 @@
       render-markdown = {
         enable = true;
       };
+
+      # Basic auto-completion
+      cmp = {
+        enable = true;
+        autoEnableSources = true;
+        
+        settings = {
+          sources = [
+            { name = "buffer"; }     # Words from open buffers
+            { name = "path"; }       # File system paths
+          ];
+          
+          mapping = {
+            "<C-Space>" = "cmp.mapping.complete()";          # Trigger completion manually
+            "<C-e>" = "cmp.mapping.close()";                 # Close completion menu
+            "<CR>" = "cmp.mapping.confirm({ select = true })"; # Accept selected completion
+            "<Tab>" = "cmp.mapping.select_next_item()";      # Navigate down in menu
+            "<S-Tab>" = "cmp.mapping.select_prev_item()";    # Navigate up in menu
+          };
+        };
+      };
     };
 
     # Extra plugins that don't have dedicated modules