Fix Intel CI env corruption and remove Python 3.14 pinning

- Replace `printenv >> $GITHUB_ENV` with a before/after diff that
  exports only vars added/changed by Intel setvars.sh. The old approach
  dumped all env vars including shell internals with special characters,
  causing "Invalid format" errors in GitHub Actions.
- Remove explicit Python 3.14 setup from test.yml and lint-toolchain.yml
  (runners already have a suitable Python).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

.github/workflows/lint-toolchain.yml

@@ -14,11 +14,6 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
-    - name: MFC Python setup
-      uses: actions/setup-python@v5
-      with:
-        python-version: '3.14'
-
     - name: Initialize MFC
       run: ./mfc.sh init
 

.github/workflows/test.yml

@@ -226,8 +226,13 @@ jobs:
             sudo add-apt-repository "deb https://apt.repos.intel.com/oneapi all main"
             sudo apt-get update
             sudo apt-get install -y intel-oneapi-compiler-fortran intel-oneapi-mpi intel-oneapi-mpi-devel
+            # Export only new/changed env vars from setvars.sh.
+            # `printenv >> $GITHUB_ENV` dumps all vars including shell internals
+            # with special characters that corrupt GITHUB_ENV parsing.
+            printenv | sort > /tmp/env_before
             source /opt/intel/oneapi/setvars.sh
-            printenv >> $GITHUB_ENV
+            printenv | sort > /tmp/env_after
+            diff /tmp/env_before /tmp/env_after | grep '^>' | sed 's/^> //' >> $GITHUB_ENV
 
       - name: Get system info for cache key
         id: sys-info