feat(inception): services/inception.decide() + current_defaults(); the standard Systems vocabulary moves to the service and seeds at inception (#2881, milestone 297 step 3)

- inception.decide(user, project, choices=, via=): owner-only; validates the
  choices (pure) and every target (owned rulebook / always-on for an
  exclusion / readable design system) BEFORE any effect; then, each
  idempotent: exclude always-on rulebooks, subscribe rulebooks, point the
  design system (None = explicitly none), seed the standard Systems if asked
  and the project has none; writes projects.inception LAST. Re-deciding is
  additive for exclusions/subscriptions, replaces the design system, never
  re-seeds.
- inception.current_defaults(): what binds if nobody decides — the ask's
  payload (always-on / other rulebooks, standing exclusions + subscriptions,
  design system + the choices, Systems count).
- services/systems.STANDARD_SYSTEMS (name + generic charter) + seed_standard_systems();
  mcp/tools/systems names the same list in the bootstrap ask — one vocabulary.
- Integration tests: effects land and the record says why; bad targets apply
  nothing; outsiders cannot decide.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/scribe/mcp/tools/systems.py

@@ -30,10 +30,10 @@ _BOOTSTRAP_TITLES = 6
 # design (rule #115): archetypes any codebase could have, never one
 # install's subsystems. Mint freely beyond the list; the duplicate gate
 # guards sprawl.
-_STANDARD_SYSTEMS = (
-    "CI & Release", "Auth & Access", "Data Model & Storage", "API Surface",
-    "UI & Design", "Import & Export", "Background Jobs", "Observability",
-)
+# The standard vocabulary lives with the service (services/systems.
+# STANDARD_SYSTEMS) since milestone 297 — the inception seed mints it and this
+# ask names it, one list for both.
+_STANDARD_SYSTEMS = tuple(name for name, _charter in systems_svc.STANDARD_SYSTEMS)
 
 
 async def bootstrap_systems_ask(user_id: int, project_id: int) -> str | None: