Add reAM250 BOM research task pack

[changbowei]

Summary

Adds the reAM250-specific one-off BOM research task pack and the first three validated research outputs.

This branch is intended for review/inspection of the task-local workflow and results, not as a generic queue-system change.

Scope

Included:

• reAM250 BOM research task instructions
• task-local result schema and validator
• queue task generator
• Codex batch runner
• targeted rerun support via --id-prefix
• STEP assembly material extraction helper
• first three validated research result files under research/ream250_bom/

Excluded:

• large local CAD gold package under design/real-mechanical/reAm250/reAM250_cad_gold_package/
• local tool installs
• unrelated local docs/status files

Notes

This task pack depends on the queue completion guards from:

fix/research-queue-output-guards

The CAD workflow is intentionally deferred: agents read the CAD file only after leasing a specific row. For material lookup, the task pack now checks
00_assembly.step material/density metadata before falling back to BOM/vendor/web evidence.

Validation

Ran:

/home/eastrolinux/seres/.venv/bin/python queue_tasks/research_mission/ream250_bom_research/research_scripts/validate_results.py --dir research/ream250_bom

/home/eastrolinux/seres/.venv/bin/python -m py_compile \
  queue_tasks/research_mission/ream250_bom_research/research_scripts/generate_queue_tasks.py \
  queue_tasks/research_mission/ream250_bom_research/research_scripts/validate_results.py \
  queue_tasks/research_mission/ream250_bom_research/research_scripts/extract_step_materials.py

Also verified runner prompt generation with --dry-run.

Result files currently validate successfully:

- ream250_bom_row_0308_174.md
- ream250_bom_row_0195_6Q.md
- ream250_bom_row_0380_4122.md