Add READMEs for components, systems, and yachtpit crates; update project overview in root README.

crates/components/README.md

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+# yachtpit/crates/components
+Provides components and rendering utilities for yachtpit.
+
+## Overview
+The `components` crate contains components and rendering primitives built on top of Bevy's engine.
+
+## Usage
+This crate is designed to be used internally within the yachtpit project and is not published to crates.io. It exports foundational components used by the `systems` and `yachtpit` crates.

crates/systems/README.md

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+# yachtpit/crates/systems
+This crate provides Bevy-based systems and logic for yachtpit.
+
+## Overview
+The `systems` crate contains the core systems and logic built on top of Bevy's engine. 
+It depends on the `components` crate and extends it with domain-specific systems, behaviors, and randomization utilities.
+
+## Usage
+This crate is designed to be used internally within the yachtpit project and is not published to crates.io. It provides the game systems layer that bridges the foundational components with the main application logic.

crates/yachtpit/README.md

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+# yachtpit/crates/yachtpit
+This is the main application crate for yachtpit.
+
+## Overview
+The `yachtpit` crate unifies components and systems into an application. 
+It supports several runtimes to include web, desktop, and mobile platforms.
+
+## Usage
+### Native
+```bash
+cargo run --features dev
+```
+### Web
+```bash
+trunk serve
+```
+### Mobile
+See the `mobile/` directory for platform-specific build instructions.