fix: address Phase 1 code-quality review findings

- Generator feature templates emit ctx-arg signatures + updated checklist
- signUpUseCase test for bus=undefined path
- di-explainer.html: bind-dev-seed no-arg → ctx
- data-flow-explainer.html: tradeoff card → ctx
- BindContextBase no longer exported
- CLAUDE.md binder bullet: drop vestigial cast guidance

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -56,7 +56,7 @@ Turborepo + pnpm monorepo organized by vertical features. Each feature (`auth`,
 - **Public surface split** — Feature root (`.`) exports contracts only: types, errors, schemas, IUseCase / IController aliases, router type, constants. UI artifacts (query builders, components) live behind `./ui` (`src/ui/index.ts`). Apps import queries from `@repo/<feature>/ui`, schemas/types from `@repo/<feature>`
 - **Payload repositories via constructor** — Feature packages receive Payload config at constructor time, not as a direct dependency
 - **Three binding modes per feature** — Each feature exports two binders: `./di/bind-production` (real Payload) and `./di/bind-dev-seed` (populated mock). The app's `bindAll()` dispatcher in `apps/web-next/src/server/bind-production.ts` picks one by env: `USE_DEV_SEED="true"` → dev seed; `NODE_ENV="production"` → production; otherwise → dev seed (developer default so `pnpm dev` boots without Payload). Dev seed lives in `src/__seeds__/dev.ts` as a lazy `buildDev<Entities>()` function that uses the feature's existing factory
-- **Binders take a `ctx` arg from `core-shared/di`** — `bindProductionX(ctx: BindProductionContext)` for production binders; `bindDevSeedX(ctx: BindContext)` for dev-seed. Required fields: `tracer`, `logger`, plus `config` for production. Optional fields: `bus`, `queue`, `realtime`, `realtimeRegistry` (correspond to optional core packages — guard with `?.` when used, or cast to the full interface if the feature unconditionally requires the dep). Aggregator builds one ctx object and passes it to all feature binders
+- **Binders take a `ctx` arg from `core-shared/di`** — `bindProductionX(ctx: BindProductionContext)` for production binders; `bindDevSeedX(ctx: BindContext)` for dev-seed. Required fields: `tracer`, `logger`, plus `config` for production. Optional fields: `bus`, `queue`, `realtime`, `realtimeRegistry` (correspond to optional core packages — guard with `?.` or `if (bus) { ... }` when used; use-case signatures should accept the protocol type when they only need protocol methods, not the full concrete interface). Aggregator builds one ctx object and passes it to all feature binders
 - **App bootstrap** — Each app calls `bindAll()` from a server entry point (page server component, route handler) before resolving any feature controller. The dispatcher is idempotent
 - **Instrumentation lives in `core-shared/instrumentation/`** — Two interfaces (`ITracer`, `ILogger`), three implementations (`NoopTracer`/`NoopLogger`, `SentryTracer`/`SentryLogger`, and `RecordingTracer`/`RecordingLogger` from `core-testing`). Feature packages MUST NOT import `@sentry/*` directly (R40, eslint-enforced)
 - **Spans + capture composed at DI bind time** — Use cases + controllers wrapped via `withSpan(tracer, spanOpts, withCapture(logger, tags, factory(deps)))` inside `bind-production` / `bind-dev-seed`. `withSpan` is outermost so an errored span's timing reflects the capture-and-rethrow. Repository methods are different — they call `this.tracer.startSpan(...)` and `this.logger.captureException(...)` inline per method because they own per-call attributes (R41, R42)