feat: add chezmoi merge tools with VSCode integration and Fish helper

- Add VSCode-based merge helper with clear visual layout explanation
- Add Fish function for fzf-based interactive conflict selection
- Update CLAUDE.md with .tmpl file search patterns and tool usage guidelines

home/dot_config/fish/functions/chmerge.fish

@@ -0,0 +1,30 @@
+function chmerge --description "Interactively merge chezmoi conflicts using fzf"
+    # Get files with merge conflicts (MM = modified in both source and target)
+    set -l conflict_files (chezmoi status | grep '^MM ' | awk '{print $2}')
+
+    if test (count $conflict_files) -eq 0
+        echo "No merge conflicts found."
+        return 0
+    end
+
+    # Use fzf for selection with multi-select enabled
+    set -l selected (printf '%s\n' $conflict_files | fzf \
+        --multi \
+        --preview 'chezmoi diff {}' \
+        --preview-window 'right:70%:wrap' \
+        --header 'Select files to merge (Tab for multi-select, Enter to confirm)' \
+        --bind 'ctrl-/:toggle-preview')
+
+    if test (count $selected) -eq 0
+        echo "No files selected."
+        return 0
+    end
+
+    # Convert to absolute target paths and merge
+    for file in $selected
+        # Expand ~ to home directory for chezmoi merge
+        set -l target_path (string replace -r '^~' $HOME $file)
+        echo "Merging: $file"
+        chezmoi merge $target_path
+    end
+end