docs: give architecture review rules a per-artifact home

Move `docs/defensive-patterns.md` into `docs/defensive-patterns/`, one page per
artifact plus a README router, and state each rule as its requirement, the
condition a reviewer judges it by, its boundary and approver, and a correct and
a wrong example.

- `general.md` (the moved page): the existing bug-class rules plus timing,
  value representation, shared-state ownership, decentralization, performance
  evidence, and migrations.
- `package-surface.md`, `remote-and-api.md`, `client-components.md`,
  `conversation-and-session.md`: the review requirements for those artifacts,
  linking type definitions and semantics to `docs/subsystems/` instead of
  restating them.
- `README.md`: the habits behind the rules and the route from artifact to page.
- `dsh-code-review` reads the owning pages before judging a diff; the
  `dsh-architecture-discipline` routing skill is retired in favour of the
  directory, and every inbound reference is repaired.
- Chinese counterparts, pairing records, and the documentation tier table are
  updated together.

docs/api-gateway.md

@@ -163,3 +163,9 @@ Remote handles unary method calls with one request and one result, and stream me
 The API layers are organized as `remotes → gateway → connection → webserver`. The BFF and Typert RPC layers live under `packages/api`; Connection and WebServer live at `packages/client/connection` and `packages/host/webserver`. Unary results containing `Uint8Array`, including nested fields and array entries, use [binary Remote transfer](../.agents/notes/implemented/architecture/2026-09-17-workspace-file-binary-transfer.md). A feature that needs a response outside the RPC envelope registers an exact Connection Fetch route.
 
 Lookup policy is configured per key, so all `agent` or `session` parameters share the cold-resume behavior. Accepting live objects only would require an explicit per-parameter or per-endpoint policy, which does not exist; the business method must not guess whether the object came from restoration.
+
+### Business ownership
+
+`packages/api` owns transport, call shape, and session lifecycle. A business rule — a state-dependent decision, a feature-specific handling path, or a per-feature filter — belongs to an independent business package and reaches this layer through a registration surface or projected data. A new business branch here needs an independent-package review.
+
+A new remote capability declares its own service instead of growing an existing one, marks the capability method with `@Remote`, and leaves client-facing types to inference. Remote payloads stay JSON with no output-side decode, and existing method and field names are additive.