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_rule_usage_wiring.py

@@ -330,7 +330,6 @@ def test_rules_payload_records_both_the_family_and_project_halves():
                 "rules": [{"id": 10}, {"id": 11}],
                 "project_rules": [{"id": 12}],
                 "truncated": False,
-                "subscribed_rulebooks": [],
             },
             user_id=1,
             source="enter_project",
@@ -342,9 +341,9 @@ def test_rules_payload_records_both_the_family_and_project_halves():
 
 
 def test_brief_rules_payload_lists_titles_and_records_only_what_it_shows():
-    """The handshake's form (#4045): project rules by id and title, the
-    subscribed rulebooks, nothing else. A subscription-derived rule it doesn't
-    show must not count as surfaced."""
+    """The handshake's form (#4045): project rules by id and title, nothing
+    else (subscriptions went in milestone 414). A global rule it doesn't show
+    must not count as surfaced."""
     from scribe.services import rulebooks as svc
 
     rec = MagicMock()
@@ -354,17 +353,13 @@ def test_brief_rules_payload_lists_titles_and_records_only_what_it_shows():
                 "rules": [{"id": 10, "title": "family", "statement": "s"}],
                 "project_rules": [{"id": 12, "title": "own", "statement": "s"}],
                 "truncated": False,
-                "subscribed_rulebooks": [{"id": 1, "title": "Family"}],
             },
             user_id=1,
             source="enter_project",
             brief=True,
         )
 
-    assert out == {
-        "project_rules": [{"id": 12, "title": "own"}],
-        "subscribed_rulebooks": [{"id": 1, "title": "Family"}],
-    }
+    assert out == {"project_rules": [{"id": 12, "title": "own"}]}
     assert rec.call_args.kwargs["rule_ids"] == [12]