feat: add work import schema

[solomonneas]

Summary

• document the work import JSONL schema for scanners and wrappers
• add import validate and ingest commands with duplicate pending-import protection
• add a memory-care refresh queue producer for local task imports

Verification

• .venv/bin/python -m pytest tests/test_work_cmd.py -q
• .venv/bin/brigade work import validate tmp-import-smoke.jsonl
• .venv/bin/brigade work import ingest tmp-import-smoke.jsonl
• .venv/bin/brigade work import ingest tmp-import-smoke.jsonl
• .venv/bin/brigade work import memory-care --queue tmp-memory-care-refresh-queue.json
• .venv/bin/brigade work import triage --limit 5
• .venv/bin/brigade work import dismiss --reason "smoke cleanup"
• .venv/bin/python -m pytest -q
• PYTHONPATH=$HOME/repos/content-guard/src python3 -m content_guard scan . --policy $HOME/repos/content-guard/policies/public-repo.json
• git diff --check