CI: Run encoding tests in single batch instead of for loop

Simplify the functional-testing workflow to run all encoding tests
at once rather than iterating through each test individually. This
matches how qa/bin/test_everything runs the tests and is more efficient.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: thomas-mangin

.github/workflows/functional-testing.yml

@@ -45,11 +45,7 @@ jobs:
 
       - name: Functional
         run: |
-          # Get list of all test identifiers and run them sequentially
-          for test in $(uv run ./qa/bin/functional encoding --short-list); do
-            echo "Running test: $test"
-            uv run ./qa/bin/functional encoding "$test"
-          done
+          uv run ./qa/bin/functional encoding
 
       - name: Decoding
         run: |