chore: import upstream snapshot with attribution

.cursor/rules/sim-architecture.mdc

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+---
+description: Core architecture principles for the Sim app
+globs: ["apps/sim/**"]
+---
+# Sim App Architecture
+
+## Core Principles
+1. **Single Responsibility**: Each component, hook, store has one clear purpose
+2. **Composition Over Complexity**: Break down complex logic into smaller pieces
+3. **Type Safety First**: TypeScript interfaces for all props, state, return types
+4. **Predictable State**: Zustand for global state, useState for UI-only concerns
+
+## Root-Level Structure
+
+```
+apps/
+├── sim/                 # this app (Next.js: UI + API routes + workflow editor)
+│   ├── app/             # Next.js app router (pages, API routes)
+│   ├── blocks/          # Block definitions and registry
+│   ├── components/      # Shared UI (emcn/, ui/)
+│   ├── executor/        # Workflow execution engine
+│   ├── hooks/           # Shared hooks (queries/, selectors/)
+│   ├── lib/             # App-wide utilities
+│   ├── providers/       # LLM provider integrations
+│   ├── stores/          # Zustand stores
+│   ├── tools/           # Tool definitions
+│   └── triggers/        # Trigger definitions
+└── realtime/            # Bun Socket.IO server (collaborative canvas)
+
+packages/                # @sim/* — audit, auth, db, logger, realtime-protocol,
+                         # security, tsconfig, utils, platform-authz,
+                         # workflow-persistence, workflow-types
+```
+
+## Package Boundaries
+
+- `apps/* → packages/*` only. Packages never import from `apps/*`.
+- `apps/realtime` avoids Next.js, React, the block/tool registry, provider SDKs, and the executor; never add `@/lib/webhooks/providers/*`, `@/executor/*`, `@/blocks/*`, or `@/tools/*` imports to any package it consumes. CI enforces this via `scripts/check-monorepo-boundaries.ts` and `scripts/check-realtime-prune-graph.ts`.
+
+## Feature Organization
+
+Features live under `app/workspace/[workspaceId]/`:
+
+```
+feature/
+├── components/          # Feature components
+├── hooks/               # Feature-scoped hooks
+├── utils/               # Feature-scoped utilities (2+ consumers)
+├── feature.tsx          # Main component
+└── page.tsx             # Next.js page entry
+```
+
+## Naming Conventions
+- **Components**: PascalCase (`WorkflowList`)
+- **Hooks**: `use` prefix (`useWorkflowOperations`)
+- **Files**: kebab-case (`workflow-list.tsx`)
+- **Stores**: `stores/feature/store.ts`
+- **Constants**: SCREAMING_SNAKE_CASE
+- **Interfaces**: PascalCase with suffix (`WorkflowListProps`)
+
+## Utils Rules
+
+- **Never create `utils.ts` for single consumer** - inline it
+- **Create `utils.ts` when** 2+ files need the same helper
+- **Check existing sources** before duplicating (`lib/` has many utilities)
+- **Location**: `lib/` (app-wide) → `feature/utils/` (feature-scoped) → inline (single-use)