Add user goal variations

[marksibrahim]

• adds 9 additional rephrases of task goals in 3 different styles: casual, formal, and unrelated context.
• Each task now has 10 goal phrasings -> total of 270 unique goals.
• all rewrites (should) capture the same intent
• updates documentation to describe new goal reformulations and new configs

Test verification

Confirmed both:

uv run launch_parallel_agents.py \
  --config-name=config_parallel_tasks_across_goal_variations mode=local
  
uv run launch_parallel_agents.py --config-name=config_parallel_tasks_across_goal_variations mode=internal-fair-sc-3-cpu agent=GPT-5.5-screen-and-text