docs: add missing research grants references

[Bortlesboat]

Summary

• add the missing research-grants reference docs for budget, funding mechanisms, methods, resubmission, review criteria, team building, and timeline planning
• add a regression test that checks referenced research-grants markdown files exist

Validation

• uv run --no-sync pytest tests/test_research_grants_references.py -q
• git diff --check

Fixes #118