docs: refresh package list + Read first refs after optional-package extraction

- CLAUDE.md project-overview lists must-have core packages (shared/cms/api)
  separately from the four optionals (realtime/events/trpc/ui) with their
  scaffold command. Read first list adds template-tiers.md and notes that
  the events + realtime guides require their package to be scaffolded first.
- overview.md "Five tags" updated: core-composition is 2 must-have plus
  trpc (optional); core is 1 must-have plus ui/realtime/events (optional).
- dependency-flow.md fix: replaces the stale `// in packages/core-trpc`
  example with `// in packages/core-shared` (core-trpc is now optional and
  may not exist in a slim template).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/architecture/overview.md

@@ -94,11 +94,13 @@ Both use the same five-tag model; see "Five tags" section below.
 The workspace is organized into five mutually exclusive tags:
 
 - **app** (4 packages): `apps/cms`, `apps/web-next`, `apps/web-tanstack`, `apps/storybook`
-- **core-composition** (3 packages): `packages/core-api`, `packages/core-cms`, `packages/core-trpc`
-- **core** (2 packages): `packages/core-shared`, `packages/core-ui`
+- **core-composition** (2 must-have): `packages/core-api`, `packages/core-cms`. Plus `packages/core-trpc` when scaffolded via `pnpm turbo gen core-package trpc` (optional).
+- **core** (1 must-have): `packages/core-shared`. Plus `packages/core-ui`, `packages/core-realtime`, `packages/core-events` when scaffolded via `pnpm turbo gen core-package <name>` (optional).
 - **feature** (5 packages): `packages/auth`, `packages/blog`, `packages/media`, `packages/marketing-pages`, `packages/navigation`
 - **tooling** (2 packages): `packages/core-eslint`, `packages/core-typescript`
 
+See `docs/architecture/template-tiers.md` for the must-have/optional split and the scaffold commands.
+
 **Allowed dependency directions:**
 
 | Tag | May depend on |