docs(adr): add ADRs 006-009 for vertical refactor

docs/decisions/adr-009-integrations-folder-naming.md

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+# ADR-009: Rename `adapters/` to `integrations/`
+
+**Status:** Accepted
+**Date:** 2026-05-04
+
+## Context
+
+The source spec (monorepo-architecture-spec-detailed-v5.md) uses `adapters/cms` and `adapters/api` for Payload and tRPC integration points. Clean Architecture also uses `adapters/` (or `interface-adapters/`) for transport-agnostic controller layer. The name collision is confusing.
+
+## Decision
+
+Use `integrations/` for role-based plug points (Payload and tRPC). Keep `interface-adapters/` for the Clean Architecture controller layer.
+
+**Result:**
+```
+packages/<feature>/src/
+  interface-adapters/controllers/  ← Clean Architecture layer (transport-agnostic)
+  integrations/
+    cms/                           ← Payload collections/globals
+    api/                           ← tRPC routers
+```
+
+## Consequences
+
+- No naming collision — intent is unambiguous
+- `integrations/` semantically captures "external system integration" better than `adapters/`
+- Minor deviation from source spec, documented here as deliberate choice
+- All new features follow this naming consistently
+
+## Alternatives Considered
+
+- Keep `adapters/`: Collision with Clean Architecture terminology is confusing
+- Use `external/`: Less specific; doesn't convey "Payload and tRPC"
+- Rename Clean Architecture layer to `controllers/`: Could work; less standard