feat: add housekeeper control plane and isolated media jobs

[nxs9bg24js-tech]

Clean mainline transplant of PR #19 onto current main.

Scope

• add the housekeeper control plane with persisted mode state, admission checks, night budgets, dedup, circuit breaker, and morning summaries
• add isolated media jobs plus narrow Telegram routing for explicit media requests
• wire the new execution profiles into planner and manager entrypoints without rewriting the existing execution chain
• add systemd units and focused housekeeper/media coverage

Clean-base note

• this branch is cherry-picked from the PR RFC: add 7x24 housekeeper control plane and isolated media jobs #19 RFC implementation onto latest main
• diff intentionally excludes the codex/docs-cc-switch-workstation base-only changes

Validation run locally

• PYTHONPATH=src /Volumes/AI_LAB/Github/autonomous-agent-stack/.venv/bin/pytest -q tests/test_housekeeper.py tests/test_media_jobs.py tests/test_manager_agent.py tests/test_autoresearch_planner.py tests/test_gateway_telegram.py
• result: 48 passed in 10.96s
• PYTHONPATH=src /Volumes/AI_LAB/Github/autonomous-agent-stack/.venv/bin/pytest -q tests/gateway/test_message_mirror.py tests/test_agent_protocol_models.py tests/test_agent_policy_merge.py tests/test_agent_runner_patch_filter.py tests/test_agent_fallbacks.py tests/test_approvals_api.py tests/test_capability_api.py tests/test_gatekeeper_e2e.py tests/test_openclaw_compat.py tests/test_openhands_controlled_backend.py
• result: 57 passed in 19.30s

CI note

• GitHub CI currently inherits existing repo-wide core lint/black debt already present on main paths outside this RFC slice
• this PR is kept draft until we decide whether to absorb that baseline hygiene here or clear it separately