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_milestone_summary_brief.py

@@ -80,8 +80,7 @@ def _task(tid: int, milestone_id: int | None) -> MagicMock:
 
 def _enter_stubs(project, milestones: list[dict], tasks: list, *, rules=None, systems=None,
                  design=None):
-    applicable = rules or {"rules": [], "project_rules": [], "truncated": False,
-                           "subscribed_rulebooks": []}
+    applicable = rules or {"rules": [], "project_rules": [], "truncated": False}
     return [
         patch("scribe.mcp.tools.projects.projects_svc.get_project",
               AsyncMock(return_value=project)),
@@ -121,8 +120,7 @@ async def test_enter_project_stays_small_however_large_the_project():
         "rules": [{"id": i, "title": f"r{i}", "statement": PLAN} for i in range(50)],
         "project_rules": [{"id": 100 + i, "title": f"pr{i}", "statement": PLAN,
                            "when_to_apply": PLAN} for i in range(60)],
-        "truncated": True, "subscribed_rulebooks": [{"id": 1, "title": "Family"}],
-        "suppressed_rules": [], "suppressed_topics": [],
+        "truncated": True,
     }
     systems = []
     for i in range(40):
@@ -181,8 +179,7 @@ async def test_get_project_lists_every_milestone_without_plans():
          patch("scribe.mcp.tools.projects.milestones_svc.get_project_milestone_summary",
                AsyncMock(return_value=_history(10))), \
          patch("scribe.mcp.tools.projects.rulebooks_svc.get_applicable_rules",
-               AsyncMock(return_value={"rules": [], "truncated": False,
-                                       "subscribed_rulebooks": []})):
+               AsyncMock(return_value={"rules": [], "truncated": False})):
         out = await get_project(project_id=5)
     assert len(out["milestone_summary"]) == 10
     assert all("body" not in m for m in out["milestone_summary"])