feat(rules)!: retire rulebook subscriptions and per-project suppressions (#4052)

A rule's home is its scope now: a rule in a rulebook topic is global, a rule on
a project applies to that project, and retrieval reads that directly (#4074).
A subscription had stopped changing anything a session received; a suppression
muted rules from a subscription. Operator, 2026-09-15: "we have global and
project scoped rules, we don't need the subscriptions now."

What goes, whole (rule 22):
- Migration 0101 drops project_rulebook_subscriptions, project_rule_suppressions
  and project_topic_suppressions, and strips subscribe_rulebooks (and 394's
  leftover exclude_always_on_rulebooks) from stored inception choices.
- Service, MCP and REST: subscribe/unsubscribe and the four suppress/unsuppress
  operations. The Subscribers checklist, the subscribe chips, the skip buttons
  and the Suppressed section in the rules UI.
- Inception asks two questions (design system, seed Systems). create_project and
  decide_project_inception lose subscribe_rulebooks.
- Backup v15 stops exporting the three sections; older archives still restore,
  the keys simply unread. Trash no longer hard-deletes suppression rows.

What changes meaning:
- get_applicable_rules is a project's LISTING: its own rules, plus the global
  rules tagged to an area it works in. Untagged global rules apply everywhere
  and arrive by retrieval, so they are not listed. A co_surfaces partner on a
  different project is not dragged in.
- list_rules(project_id) lists that project's own rules.
- rules_payload drops subscribed_rulebooks and suppressed_*; the handshake's
  brief form is project_rules alone.
- using-scribe's "Where a new rule goes" and inception sections, tool
  docstrings and docs say global vs project. Plugin 2026.09.15.1620.

Milestone 414 step 2.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

tests/test_services_trash.py

@@ -44,16 +44,15 @@ async def test_delete_returns_none_when_not_found():
 
 
 @pytest.mark.asyncio
-async def test_delete_project_cascades_to_notes_milestones_project_rules_and_suppressions():
+async def test_delete_project_cascades_to_notes_milestones_and_project_rules():
     session = make_mock_session()
-    # exists-check + 6 cascade ops:
+    # exists-check + 4 cascade ops:
     #   notes (soft) → milestones (soft) → project-scoped rules (soft) →
-    #   project_rule_suppressions (hard DELETE) → project_topic_suppressions (hard DELETE) →
     #   project (soft)
+    # The two suppression hard-DELETEs went with their tables (milestone 414).
     session.execute = AsyncMock(side_effect=[
         _exists_result(True),
         MagicMock(), MagicMock(), MagicMock(),
-        MagicMock(), MagicMock(),
         MagicMock(),
     ])
     with patch("scribe.services.trash.async_session") as cls:
@@ -61,7 +60,7 @@ async def test_delete_project_cascades_to_notes_milestones_project_rules_and_sup
         from scribe.services.trash import delete
         batch = await delete(user_id=1, entity_type="project", entity_id=3)
     assert isinstance(batch, str)
-    assert session.execute.await_count == 7
+    assert session.execute.await_count == 5
 
 
 @pytest.mark.asyncio