docs: Write quetza docs

services/docs/content/en/quetza/concepts/architecture.md

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+---
+title: Architecture & Philosophy
+weight: 1
+---
+
+
+**Goal:** Understand the core design principles that drive Quetza's modularity.
+
+## Design Philosophies
+
+### Convention Over Configuration
+Quetza minimizes boilerplate by relying on strict folder structures.
+*   **No central registry:** The filesystem *is* the registry.
+*   **Result:** You don't update a config file to add a module; you just create the folder.
+
+### Composition Over Inheritance
+Modules are composed of capabilities, not inherited from a base class.
+*   **Flexibility:** Modules can use any internal architecture (Functional, OOP) as long as they export the required interfaces.
+
+### Isolation Over Integration
+Modules cannot directly invoke each other.
+*   **Why:** Prevents tight coupling.
+*   **Benefit:** You can delete any module without breaking the rest of the bot.
+
+## Core Entities
+
+| Entity | Role | Lifecycle |
+| :--- | :--- | :--- |
+| **Client** | Service Locator & Orchestrator | Singleton. Runs the show. |
+| **Module** | Namespace for features | Loaded at startup. |
+| **Command** | User Interaction Endpoint | Stateless. Request/Response. |
+| **Event** | Reactive Observer | Subscribed at startup. |
+| **Controller** | State Manager | Persists across interactions. |
+
+---
+**See also:**
+- [Service Locator Pattern](https://en.wikipedia.org/wiki/Service_locator_pattern)
+- [Observer Pattern](https://en.wikipedia.org/wiki/Observer_pattern)