feat: refactor plugin architecture, enhance linting, CI & tooling

- Major refactor of core Fish functions for modularity, caching, and error handling
- Improved `.editorconfig` and Makefile for stricter formatting and linting standards
- Expanded linting support: added EditorConfig checks, auto-install for missing tools, and Makefile targets
- Enhanced CI workflow with clearer permissions and job steps in GitHub Actions
- Updated documentation in `README.md` and `CLAUDE.md` to reflect new features, advanced developer tools, and contribution guidelines
- Improved Node.js version manager detection, switching, and installation logic
- Added/updated utility functions for configuration, silent mode, notifications, and version extraction
- Various bug fixes, code quality improvements, and expanded test coverage

functions/nvm_async.fish

@@ -0,0 +1,106 @@
+function nvm_async -d "Async operations for non-blocking version management"
+    set -l operation $argv[1]
+    switch $operation
+        case version_check
+            _nvm_async_version_check $argv[2]
+        case manager_check
+            _nvm_async_manager_check $argv[2]
+        case cleanup
+            _nvm_async_cleanup
+        case wait
+            _nvm_async_wait $argv[2] $argv[3]
+        case '*'
+            echo "Usage: nvm_async [version_check|manager_check|cleanup|wait] [args...]"
+            return 1
+    end
+end
+
+function _nvm_async_version_check -d "Async version check operation"
+    set -l version_file $argv[1]
+    set -l cache_key (_nvm_cache_key "$version_file")
+
+    # Try cache first
+    if set -l cached_result (nvm_cache get "$cache_key" 60)
+        echo "$cached_result"
+        return 0
+    end
+
+    # Background job for version extraction
+    fish -c "
+        set result (nvm_extract_version '$version_file' 2>/dev/null)
+        if test -n \"\$result\"
+            nvm_cache set '$cache_key' \"\$result\"
+            echo \"\$result\"
+        end
+    " &
+
+    # Return job ID for potential cleanup
+    jobs -l | tail -n 1 | grep -o '[0-9]*'
+end
+
+function _nvm_async_manager_check -d "Async manager availability check"
+    set -l manager $argv[1]
+    set -l cache_key (_nvm_cache_manager_key "$manager")
+
+    # Try cache first (longer TTL for manager availability)
+    if set -l cached_result (nvm_cache get "$cache_key" 3600)
+        echo "$cached_result"
+        return 0
+    end
+
+    # Background check
+    fish -c "
+        if command -q '$manager'
+            nvm_cache set '$cache_key' 'available'
+            echo 'available'
+        else
+            nvm_cache set '$cache_key' 'unavailable'
+            echo 'unavailable'
+        end
+    " &
+
+    jobs -l | tail -n 1 | grep -o '[0-9]*'
+end
+
+function _nvm_async_cleanup -d "Clean up completed background jobs"
+    for job in (jobs -p)
+        if not kill -0 $job 2>/dev/null
+            jobs -p | grep -v $job
+        end
+    end
+end
+
+function _nvm_async_wait -d "Wait for async job with timeout"
+    set -l job_id $argv[1]
+    set -l timeout $argv[2]
+
+    if test -z "$timeout"
+        set timeout 2
+    end
+
+    # Wait for job with timeout
+    set -l count 0
+    while test $count -lt (math "$timeout * 10")
+        if not jobs -p | grep -q "^$job_id\$"
+            return 0
+        end
+        sleep 0.1
+        set count (math "$count + 1")
+    end
+
+    # Timeout reached, kill job
+    kill -9 $job_id 2>/dev/null
+    return 1
+end
+
+function _nvm_async_safe_read -d "Safely read async operation result"
+    set -l cache_key $argv[1]
+    set -l fallback $argv[2]
+
+    set -l result (nvm_cache get "$cache_key")
+    if test -n "$result"
+        echo "$result"
+    else if test -n "$fallback"
+        echo "$fallback"
+    end
+end