docs: align InferEdgeEnv portfolio positioning

[hyeokjun32]

Summary

• Aligned InferEdgeLab README and portfolio docs with the final InferEdgeEnv positioning.
• Fixed the portfolio boundary as: InferEdgeLab = validation / decision layer, InferEdgeEnv = run evidence registry / comparability layer.
• Updated Obsidian ecosystem notes separately to use the same wording.

Validation

• git diff --check
• poetry run inferedgelab portfolio-demo-check
• poetry run python3 -m pytest -q

Notes

• InferEdgeEnv remains a supporting evidence sidecar, not a Lab decision owner, leaderboard, remote runner, or validation layer.