Plugin runtime + reconcile dispatch + reftest sentinel

[luma-founder]

Summary

Closes the plugin-surface kernel commitment (PLAN.md step 11). PR #23 shipped discovery + GET /v1/plugins/types; this slice adds the runtime that turns discovered types into running plugins, and wires reconcile dispatch into the lock-toggle path. After this PR the kernel acceptance plugin path (PLAN.md §"Acceptance: kernel done" steps 11-16) passes end-to-end.

What's in

• core/curfew/plugin_runtime.py — PluginRuntime. In-memory {(type, instance_id): AssignedInstance} map, async-locked. Public surface:
  • build_instance — validate config + construct, no side effects.
  • register — add a pre-built instance to the map.
  • unassign — drop.
  • update — re-instantiate iff config changed; else just rewire users / paused.
  • dispatch_for_user — find governing instances, schedule reconcile concurrently with timeout.
  • safety_net_resync — walk every managed user, dispatch.
  • Failures caught at the reconcile boundary and audited as plugin.reconcile_failed; never raised.
• api/curfew_api/routes/plugins.py — GET/POST/PATCH/DELETE /v1/plugins. POST builds the live instance before writing the DB row so a bad config / broken plugin returns 422 / 500 without leaving an orphan row. PATCH on config re-instantiates (PLAN.md option 1); on users/paused rewires without touching __init__. All admin-gated and audited.
• api/curfew_api/routes/locks.py — schedule runtime.dispatch_for_user via FastAPI BackgroundTasks after the lock/unlock commit. HTTP response returns immediately; reconcile fires after.
• api/curfew_api/app.py — switch to FastAPI lifespan context. At startup: discover plugins, build the runtime, hydrate from plugin_assignments rows (skip + log per-row instantiation errors so one missing folder doesn't break startup), start a safety-net loop reading plugin_resync_seconds fresh each iteration. Cancels cleanly on shutdown.
• plugins/reftest-plugin/plugin.py — replace the no-op reconcile with sentinel-file logic: locked → write user's name to Config.sentinel_path; unlocked → remove it (idempotent). What the e2e test asserts against.
• core/curfew/schemas.py — PluginAssignmentRead, PluginAssignmentCreate, PluginAssignmentUpdate.
• api/tests/conftest.py — client fixture now wraps TestClient as a context manager so FastAPI lifespan fires (without it app.state.plugin_runtime would never be built). client_with_repo_plugins variant points CURFEW_PLUGINS_DIRS at the repo's plugins/ so reftest_plugin is discovered.

Notable design choices

• Build → DB → register, in that order. build_instance is split from register so the API can pre-validate + instantiate, then write the DB row, then commit the runtime mutation — keeping the in-memory map and the plugin_assignments table in lock-step even when 422/409 paths fire.
• Re-instantiate on PATCH config (PLAN.md option 1). Plugin authors keep __init__ simple; the operator gets new config without restarting curfew-core.
• Per-call timeout via asyncio.wait_for. Reads plugin_reconcile_timeout_seconds from the singleton settings row each call so PATCHes take effect without restart.
• Safety-net resync reads plugin_resync_seconds fresh each loop iteration. Same propagation pattern the agent SDK will use for agent_tick_seconds once the agent surface lands.
• Reconcile errors caught + audited, never raised. Originating HTTP request has already returned by the time the BackgroundTask runs; raising would just kill the task. plugin.reconcile_failed rows are how the operator confirms a specific reconcile succeeded.
• Hydrate on startup is forgiving. A row whose plugin folder was removed logs a warning and is skipped — the row stays in the DB so the operator can decide whether to fix the folder or unassign explicitly.

Out of scope (later features)

requirements.txt auto-install, plugin SDK helpers for HTTP retry/timeout (driven by adguard landing), target_apps on Scope (PLAN.md per-rule user config deferred until first non-kernel rule), concrete plugins (adguard, smart-plug, router-acl).

Test plan

• just check clean (ruff, ruff format, mypy, 250 pytest, 23 vitest, web build).
• New test count: 20 in test_plugin_runtime.py, 17 in test_plugins_assignments.py, 6 in test_plugins_reconcile.py (43 total).
• e2e covers kernel acceptance steps 11-16: assign reftest_plugin → lock kid1 → sentinel appears with content kid1; unlock → sentinel removed; paused plugin doesn't reconcile; safety-net resync picks up missed events; failed reconcile audited but the lock request still 200s; hydrate on startup brings rows back to life.
• Live smoke: just serve; assign reftest_plugin via curl; lock a managed kid; observe sentinel file; unlock; observe sentinel removed.