Prevent duplicate research idea portfolios

[lbx154]

Summary

• expose the runtime-owned canonical Idea portfolio path in the Engineer prompt immediately after preparation
• reject Idea-stage Planner tasks that attempt to own a competing portfolio or tournament under .argus/teams
• preserve ordinary bounded Team use and avoid false positives for non-portfolio tasks
• add regression coverage for prompt propagation and the historical duplicate-path contract

Root cause

The research runtime formed the canonical portfolio during library preparation, but only emitted an event. The Planner could still assign a different team path, and the Engineer never received the canonical root in its prompt, so it interpreted the empty alternate path as authorization to form a second portfolio.

Testing

• 69 passed in the focused vertical/portfolio/team suite
• Ruff passed on all changed files
• full suite reached 10660 passed, 61 skipped; the only six failures were missing optional SciencePlots locally
• after installing the declared plotting dependency, tests/skills/test_paper_chart_style.py: 23 passed
• git diff --check passed