docs(coding-agent): update README-NEW.md, tui.md, add new docs

- README-NEW.md: add environment variables, philosophy extras (no built-in to-dos, no background bash), session ID support, pi config command, plain git URLs, version pinning
- tui.md: fix hooks->extensions terminology, update Component interface (invalidate required, add wantsKeyRelease)
- Add new docs: settings.md, development.md, json.md
- Add screenshots: tree-view.png, doom-extension.png

packages/coding-agent/docs/development.md

@@ -0,0 +1,69 @@
+# Development
+
+See [AGENTS.md](../../../AGENTS.md) for additional guidelines.
+
+## Setup
+
+```bash
+git clone https://github.com/badlogic/pi-mono
+cd pi-mono
+npm install
+npm run build
+```
+
+Run from source:
+
+```bash
+./pi-test.sh
+```
+
+## Forking / Rebranding
+
+Configure via `package.json`:
+
+```json
+{
+  "piConfig": {
+    "name": "pi",
+    "configDir": ".pi"
+  }
+}
+```
+
+Change `name`, `configDir`, and `bin` field for your fork. Affects CLI banner, config paths, and environment variable names.
+
+## Path Resolution
+
+Three execution modes: npm install, standalone binary, tsx from source.
+
+**Always use `src/config.ts`** for package assets:
+
+```typescript
+import { getPackageDir, getThemeDir } from "./config.js";
+```
+
+Never use `__dirname` directly for package assets.
+
+## Debug Command
+
+`/debug` (hidden) writes to `~/.pi/agent/pi-debug.log`:
+- Rendered TUI lines with ANSI codes
+- Last messages sent to the LLM
+
+## Testing
+
+```bash
+./test.sh                         # Run non-LLM tests (no API keys needed)
+npm test                          # Run all tests
+npm test -- test/specific.test.ts # Run specific test
+```
+
+## Project Structure
+
+```
+packages/
+  ai/           # LLM provider abstraction
+  agent/        # Agent loop and message types  
+  tui/          # Terminal UI components
+  coding-agent/ # CLI and interactive mode
+```