doc: Move out docs from main README

docs/project-rules.md

@@ -0,0 +1,35 @@
+# Project Rules Configuration
+
+QodeAssist supports project-specific rules to customize AI behavior for your codebase. Create a `.qodeassist/rules/` directory in your project root.
+
+## Quick Start
+
+```bash
+mkdir -p .qodeassist/rules/{common,completion,chat,quickrefactor}
+```
+
+## Directory Structure
+
+```
+.qodeassist/
+└── rules/
+    ├── common/           # Applied to all contexts
+    ├── completion/       # Code completion only
+    ├── chat/            # Chat assistant only
+    └── quickrefactor/   # Quick refactor only
+```
+
+All `.md` files in each directory are automatically loaded and added to the system prompt.
+
+## Example
+
+Create `.qodeassist/rules/common/general.md`:
+
+```markdown
+# Project Guidelines
+- Use snake_case for private members
+- Prefix interfaces with 'I'
+- Always document public APIs
+- Prefer Qt containers over STL
+```
+