feat: add the autorun job runner

Runs the jobs of automation/jobs.yml under one host lock, with load and disk guards, one idle retry on a host misread, artifacts computed twice, explicit-path commits in .cache/autorun/worktree, an opt-in push (--push) and a CI circuit breaker. First jobs: nightly refresh chain, large-files asset dry run, disk cleanup and check, weekly bios integrity. install-timers writes systemd user units without enabling them.

wiki/testing-guide.md

@@ -58,6 +58,7 @@ Every module in `tests/`, by the area it guards.
 | Handheld launchers | a pty as the console, fake installer and firmware tools, stubbed PortMaster dialogs | `test_handheld_launchers`, `test_port` |
 | Running cores | parsers on fixed inputs, a libretro core built from C in the test when a compiler exists | `test_core_probe` |
 | Measurement records | a synthetic measurements repository built with git | `test_measurements` |
+| Automation runner, disk cleanup, asset sync and bit-flip repair | fake jobs, git repositories with a bare origin and session worktrees, a committed file with one bit flipped, canned CI runs in place of `gh` | `test_autorun` |
 | Truth and native export | synthetic + cached originals | `test_export_counts`, `test_export_native_layer`, `test_export_report`, `test_exporters`, `test_truth_data_dir_readers`, `test_truth_diff`, `test_truth_layout` |
 | Scrapers, upstream and provenance | inline sources, synthetic | `test_batocera_md5_list`, `test_check_freshness`, `test_contributing_text`, `test_coverage_cache`, `test_data_dir_refs`, `test_dataclass_defaults`, `test_dedup`, `test_doc_pages`, `test_doc_surfaces`, `test_elec_scrapers`, `test_fbneo_parser`, `test_find_pinned_revision`, `test_hash_merge`, `test_launchers`, `test_launchers_emudeck`, `test_launchers_recalbox`, `test_launchers_retrobat`, `test_launchers_retrodeck`, `test_launchers_retropie`, `test_launchers_rocknix`, `test_mame_devices`, `test_mame_parser`, `test_mame_ref_audit`, `test_optional_dependencies`, `test_profile_sync`, `test_prose_style`, `test_provenance`, `test_refresh_data_dirs`, `test_refresh_failures`, `test_refresh_stale`, `test_retrodeck_scraper_errors`, `test_romset_recipes`, `test_schema_semantic_gate`, `test_scraper_contract`, `test_site_availability`, `test_site_content_data`, `test_site_copy`, `test_site_cores`, `test_site_emulator_page`, `test_site_exports`, `test_site_funnel`, `test_site_images`, `test_site_picker`, `test_site_platform_hashes`, `test_site_r2_components`, `test_site_r2_css`, `test_site_r2_emulators`, `test_site_r2_entry`, `test_site_r2_gate`, `test_site_r2_nav`, `test_site_r2_p0`, `test_site_r2_reference`, `test_site_r2_systems`, `test_site_r2_wiki`, `test_site_r3_collection`, `test_site_r3_components`, `test_site_r3_css`, `test_site_r3_emulators`, `test_site_r3_entry`, `test_site_r3_nav`, `test_site_r3_p0`, `test_site_r3_reference`, `test_site_r3_systems`, `test_site_r3_wiki`, `test_site_r4_components`, `test_site_r4_css`, `test_site_r4_emulators`, `test_site_r4_entry`, `test_site_r4_merge`, `test_site_r4_p0`, `test_site_r4_reference`, `test_site_r4_search`, `test_site_r4_systems`, `test_site_r4_wiki`, `test_site_r5_components`, `test_site_r5_css`, `test_site_r5_emulators`, `test_site_r5_entry`, `test_site_r5_reference`, `test_site_r5_search`, `test_site_r5_systems`, `test_site_r5_wiki`, `test_site_render`, `test_site_system_links`, `test_site_validation`, `test_site_weight`, `test_site_write`, `test_source_ref_targets`, `test_upstream`, `test_upstream_index`, `test_validate_pr`, `test_validate_pr_flow`, `test_validate_pr_hashes`, `test_workflow_paths` |