Tighten repair prompt for blocking future followups

[wwind123]

Summary

• Treat Repair approved reviews with active prior dispositions #246 as the existing tracker for this repair-pass subcase.
• Add a hard repair-prompt constraint that any repaired blocking PR/plan review must set future_followups to an empty array.
• Add a focused blocking plan_review example showing current-plan items moved into blocking/same-plan fields and later work dropped.
• Extend prompt regression tests for the new example and constraint.

Refs #246

Tests

• /home/wwind123/tools/coding-review-agent-loop/.venv/bin/python -m pytest /home/wwind123/openai-codex/coding-review-agent-loop-repair-blocking-future/tests/test_agent_loop.py -k "repair_prompt_blocking_reviews_drop_future_followups or repair_prompt_includes_worked_example_6_to_13 or repair_prompt_example_12_same_round_confusion_case or repair_prompt_includes_approved_future_followups_current_plan_rule"
• /home/wwind123/tools/coding-review-agent-loop/.venv/bin/python -m py_compile /home/wwind123/openai-codex/coding-review-agent-loop-repair-blocking-future/src/coding_review_agent_loop/repair.py /home/wwind123/openai-codex/coding-review-agent-loop-repair-blocking-future/tests/test_agent_loop.py