fabrik exec gains –script flag, FABRIK-header autodetection, and direct shebang execution

fabrik run and fabrik exec now apply script-aware parsing to annotated script files. You can pass --script to fabrik exec to interpret argv as <runtime> <script> [args...] and read FABRIK headers from the script (e.g., fabrik exec --script bash scripts/build.sh). The same form is autodetected when argv already looks like <runtime> <script> and the file carries FABRIK headers, so a shebang line such as #!/usr/bin/env -S fabrik exec -- bash runs the script directly.