fix: Address all Homebrew style violations

Fixed all 16 style violations detected by brew style:

**Required Headers:**
- Added: # typed: true (Sorbet type checking)
- Added: # frozen_string_literal: true (Ruby optimization)
- Added: Top-level documentation comment for Mfc class

**Whitespace Issues:**
- Removed all trailing whitespace (7 locations)
- Removed trailing blank lines at end of file

**Assertion Updates:**
- Changed: assert_predicate -> assert_path_exists (5 locations)
- More idiomatic for Homebrew formulas

**CI Workflow:**
- Removed brew audit with path (now disabled in Homebrew)
- Keep brew style check which catches all these issues

All offenses are now resolved. The formula passes brew style checks.

Author: sbryngelson

.github/workflows/homebrew.yml

@@ -40,7 +40,6 @@ jobs:
       - name: Validate formula syntax
         run: |
           echo "Checking formula syntax..."
-          brew audit --strict --online packaging/homebrew/mfc.rb || true
           brew style packaging/homebrew/mfc.rb
       
       - name: Install MFC from formula

packaging/homebrew/mfc.rb

@@ -1,3 +1,7 @@
+# typed: true
+# frozen_string_literal: true
+
+# Homebrew formula for MFC (Multiphase Flow Code)
 class Mfc < Formula
   desc "Exascale multiphase/multiphysics compressible flow solver"
   homepage "https://mflowcode.github.io/"
@@ -38,10 +42,10 @@ def install
     # - bootstrap/ for build/lint/format scripts
     # - templates/ for HPC job submission
     prefix.install "toolchain"
-    
+
     # Install examples
     pkgshare.install "examples"
-    
+
     # Create a wrapper that sets up the environment and calls mfc.sh
     # The wrapper changes to the installation directory because mfc.sh
     # expects to be run from MFC's root (checks for toolchain/util.sh)
@@ -74,23 +78,22 @@ def caveats
 
   test do
     # Test that the binaries exist
-    assert_predicate bin/"pre_process", :exist?
-    assert_predicate bin/"simulation", :exist?
-    assert_predicate bin/"post_process", :exist?
-    
+    assert_path_exists bin/"pre_process"
+    assert_path_exists bin/"simulation"
+    assert_path_exists bin/"post_process"
+
     # Test mfc wrapper
     system bin/"mfc", "--help"
-    
+
     # Test that binaries can execute
     system bin/"pre_process", "-h"
     system bin/"simulation", "-h"
-    
+
     # Test that mfc.sh is accessible in libexec
-    assert_predicate libexec/"mfc.sh", :exist?
-    assert_predicate prefix/"toolchain", :exist?
-    
+    assert_path_exists libexec/"mfc.sh"
+    assert_path_exists prefix/"toolchain"
+
     # Test that mfc can parse a case file (lighter than full simulation)
     system bin/"mfc", "count", "#{pkgshare}/examples/1D_sodshocktube/case.py"
   end
 end
-