[codex] Extract PF archive import execution

[trek-e]

Summary

• move PF archive import write/report behavior into a dedicated execution module
• keep the existing run_import compatibility interface as plan-build plus execution delegation
• add execution-level tests for existing-NPC skip behavior and dialogue/report writes
• document the PF Archive Import Execution domain term in CONTEXT.md

Validation

• uv run ruff check CONTEXT.md modules/pathfinder/app/pf_archive_import.py modules/pathfinder/app/pf_archive_import_execution.py modules/pathfinder/tests/test_pf_archive_import_execution.py modules/pathfinder/tests/test_pf_archive_import_alias.py modules/pathfinder/tests/test_pf_archive_import_integration.py
• cd modules/pathfinder && uv run pytest tests/test_pf_archive_import_execution.py tests/test_pf_archive_import_plan.py tests/test_pf_archive_import_alias.py tests/test_pf_archive_import_integration.py tests/test_pf_archive_router.py tests/test_pf_archive_router_synthetic.py
• cd modules/pathfinder && uv run pytest

Notes

• no uv.lock files changed in this branch