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

docs/api-reference.md

@@ -77,7 +77,7 @@ endpoint at `/mcp`, not these REST routes.
 |--------|------|-------------|
 | GET / POST | `/api/projects` | List (owned + shared) / create |
 | GET / PATCH / DELETE | `/api/projects/:id` | Read (with `milestone_summary`, `inception`) / update / delete |
-| POST | `/api/projects/:id/inception` | Record what the project inherits `{choices: {subscribe_rulebooks, design_system_id, seed_systems}}` (owner-only; `POST /api/projects` accepts the same under `inception`) |
+| POST | `/api/projects/:id/inception` | Record what the project inherits `{choices: {design_system_id, seed_systems}}` (owner-only; `POST /api/projects` accepts the same under `inception`) |
 | GET | `/api/projects/:id/inception/defaults` | What binds if nobody decides — the inception card's payload |
 | GET | `/api/projects/:id/notes` | Notes + tasks in this project |
 | GET / POST | `/api/projects/:id/milestones` | List / create milestones |
@@ -115,11 +115,8 @@ endpoint at `/mcp`, not these REST routes.
 | GET | `/api/rules` | List rules |
 | POST | `/api/rulebook-topics/:tid/rules` | Add a rule to a topic |
 | GET / PATCH / DELETE | `/api/rules/:id` | Read / update / delete a rule |
-| POST | `/api/projects/:id/rulebook-subscriptions` | Subscribe a project to a rulebook |
-| GET | `/api/projects/:id/rules` | Applicable rules for a project |
+| GET | `/api/projects/:id/rules` | A project's own rules, and the global rules tagged to its areas |
 | POST | `/api/projects/:id/rules` | Create a project-scoped rule |
-| POST / DELETE | `/api/projects/:id/suppressions/rules/:rid` | Suppress / unsuppress a rule |
-| POST / DELETE | `/api/projects/:id/suppressions/topics/:tid` | Suppress / unsuppress a topic |
 
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