Replace brew test with direct test commands

Problem: `brew test` requires strict version matching between installed
formula and tap's git history, which is difficult to satisfy with
temporary taps. Repeated failures with "Testing requires the latest
version" error.

Solution: Skip `brew test` wrapper entirely and run test commands
directly. This approach:

1. Removes unnecessary git commit step (no longer needed)
2. Consolidates all tests into one comprehensive step
3. Tests match the formula's test block exactly:
   - Binary existence and executability
   - Installation structure (mfc.sh, toolchain)
   - Python venv setup
   - Examples installation
   - mfc wrapper functionality (--help, count)
4. Removes redundant "Verify installation structure" step
5. Still runs full simulation test case

This is more robust and avoids Homebrew's internal version checking
mechanisms that aren't designed for temporary tap workflows.

Author: sbryngelson

.github/workflows/homebrew.yml

@@ -50,12 +50,6 @@ jobs:
           echo "Copying formula to tap..."
           cp packaging/homebrew/mfc.rb $(brew --repository)/Library/Taps/mflowcode/homebrew-test/Formula/mfc.rb
           
-          echo "Committing formula to tap..."
-          cd $(brew --repository)/Library/Taps/mflowcode/homebrew-test
-          git add Formula/mfc.rb
-          git commit -m "Add MFC formula"
-          cd -
-          
           echo "Installing MFC from local tap..."
           brew install --build-from-source --verbose mflowcode/test/mfc 2>&1 | tee /tmp/brew-install.log
       
@@ -87,31 +81,43 @@ jobs:
             ~/Library/Logs/Homebrew/mfc/
           if-no-files-found: ignore
 
-      - name: Run formula tests
-        run: |
-          echo "Running Homebrew formula tests..."
-          brew test --verbose mflowcode/test/mfc
-      
-      - name: Test MFC binaries
-        run: |
-          echo "Verifying binaries are in PATH and executable..."
-          which mfc
-          which pre_process
-          which simulation
-          which post_process
-          test -x $(which mfc)
-          test -x $(which pre_process)
-          test -x $(which simulation)
-          test -x $(which post_process)
-          echo "All binaries are accessible and executable!"
-      
-      - name: Test MFC wrapper functionality
+      - name: Test MFC installation
         run: |
-          echo "Testing mfc command..."
+          echo "=== Testing MFC Installation ==="
+          
+          echo "1. Checking binaries exist and are executable..."
+          test -f $(brew --prefix)/bin/mfc && test -x $(brew --prefix)/bin/mfc
+          test -f $(brew --prefix)/bin/pre_process && test -x $(brew --prefix)/bin/pre_process
+          test -f $(brew --prefix)/bin/simulation && test -x $(brew --prefix)/bin/simulation
+          test -f $(brew --prefix)/bin/post_process && test -x $(brew --prefix)/bin/post_process
+          echo "  ✓ All binaries exist and are executable"
+          
+          echo "2. Verifying installation structure..."
+          test -f $(brew --prefix)/libexec/mfc.sh
+          test -d $(brew --prefix)/share/mfc/toolchain
+          test -d $(brew --prefix)/share/mfc/toolchain/mfc
+          echo "  ✓ Installation structure verified"
+          
+          echo "3. Checking Python venv..."
+          test -d $(brew --prefix)/Cellar/mfc/*/libexec/venv
+          test -f $(brew --prefix)/Cellar/mfc/*/libexec/venv/bin/python
+          test -f $(brew --prefix)/Cellar/mfc/*/libexec/venv/bin/pip
+          echo "  ✓ Python venv exists"
+          
+          echo "4. Checking examples..."
+          test -d $(brew --prefix)/share/mfc/examples
+          test -f $(brew --prefix)/share/mfc/examples/1D_sodshocktube/case.py
+          echo "  ✓ Examples installed"
+          
+          echo "5. Testing mfc wrapper..."
           mfc --help
+          echo "  ✓ mfc --help succeeded"
           
-          echo "Counting example cases..."
+          echo "6. Testing mfc count..."
           mfc count $(brew --prefix)/share/mfc/examples/1D_sodshocktube/case.py
+          echo "  ✓ mfc count succeeded"
+          
+          echo "=== All tests passed! ==="
       
       - name: Run MFC test case
         run: |
@@ -124,23 +130,6 @@ jobs:
           
           echo "Test case completed successfully!"
       
-      - name: Verify installation structure
-        run: |
-          echo "Checking installed files..."
-          ls -la $(brew --prefix)/bin/mfc
-          ls -la $(brew --prefix)/bin/pre_process
-          ls -la $(brew --prefix)/bin/simulation
-          ls -la $(brew --prefix)/bin/post_process
-          ls -la $(brew --prefix)/libexec/mfc.sh
-          ls -la $(brew --prefix)/share/mfc/examples/
-          
-          echo "Checking Python venv..."
-          ls -la $(brew --prefix)/Cellar/mfc/*/libexec/venv/
-          $(brew --prefix)/Cellar/mfc/*/libexec/venv/bin/python --version
-          $(brew --prefix)/Cellar/mfc/*/libexec/venv/bin/pip list | grep -E "(cantera|mfc)"
-          
-          echo "Installation verified successfully!"
-      
       - name: Uninstall and cleanup
         if: always()
         run: |