fix(workflows): update Codex CLI command to use exec subcommand

- Replaced `--full-auto` with `exec` in the Codex CLI command.
- Ensures compatibility with the updated Codex CLI syntax for executing instructions.

Author: hazadus

.github/workflows/codex.yml

@@ -56,7 +56,7 @@ jobs:
           git checkout -b $BRANCH_NAME
 
           # Use the configured GitHub Models provider
-          codex --full-auto "$INSTRUCTION"
+          codex exec "$INSTRUCTION"
           
           if [[ -n $(git status --porcelain) ]]; then
             git config user.name "GitHub Models Codex Bot"