Make clean.sh scripts executable from any directory

[k4rtikx]

Fix clean.sh scripts so they can be executed from any directory.

Many case-level clean.sh scripts source ../../tools/cleaning-tools.sh using
relative paths. When invoked from outside their directory (e.g.
./fluid-openfoam/clean.sh), the working directory differs and the relative
path breaks.

This PR ensures scripts always execute from their own directory by adding:

SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
cd "$SCRIPT_DIR"

Changes:

• Added SCRIPT_DIR handling to 111 case-level clean.sh scripts
• Updated partitioned-heat-conduction-direct/clean-tutorial.sh
  (the only non-symlink clean-tutorial.sh)
• Added missing set -e -u to
  flow-around-controlled-moving-cylinder/solid-python/clean.sh
• Left 34 symlinked clean-tutorial.sh files unchanged

Verification:

• Spot-checked scripts across multiple tutorials
• Tested running scripts from parent directories