docs: update desktop platform docs

Document macOS and Windows desktop support
Add Electron desktop development README
Refresh contributing scripts and platform notes

CONTRIBUTING.md

@@ -10,37 +10,91 @@ bun install
 
 ## Dev Scripts
 
+Run commands from the project root unless a section says otherwise.
+
 ### Web
 
 | Script | Description | Ports |
 |--------|-------------|-------|
+| `bun run dev` | Default web HMR dev flow. | auto-selected dev ports |
 | `bun run dev:web:full` | Build watcher + Express server. No HMR — manual refresh after changes. | `3001` (server + static) |
 | `bun run dev:web:hmr` | Vite dev server + Express API. **Open the Vite URL for HMR**, not the backend. | `5180` (Vite HMR), `3902` (API) |
+| `bun run start:web` | Start the packaged web server. | `3000` by default |
 
 Both are configurable via env vars: `OPENCHAMBER_PORT`, `OPENCHAMBER_HMR_UI_PORT`, `OPENCHAMBER_HMR_API_PORT`.
 
 ### Desktop (Electron)
 
 ```bash
-bun run electron:dev
+bun run electron:dev          # HMR web UI + Electron shell
+bun run electron:dev:bundled  # Electron shell using built web assets
+bun run electron:build        # Package desktop app for the current platform
 ```
 
-Launches the Electron desktop shell in dev mode.
+Desktop supports macOS and Windows. The build output is written to `packages/electron/dist`.
+
+macOS builds create `dmg` and `zip` files. You need Xcode/build tools for notarized packaging and icon asset work.
+
+Windows builds create an NSIS installer. If signing env vars are not set, the build script makes an unsigned installer.
+
+For desktop-specific details, see [`packages/electron/README.md`](./packages/electron/README.md).
 
 ### VS Code Extension
 
 ```bash
-bun run vscode:dev    # Watch mode (extension + webview rebuild on save)
+bun run vscode:dev      # Watch mode + Extension Development Host
+bun run vscode:build    # Build extension + webview
+bun run vscode:package  # Create a local .vsix package
 ```
 
-To test in VS Code:
-```bash
-bun run vscode:build && code --extensionDevelopmentPath="$(pwd)/packages/vscode"
-```
+`bun run vscode:dev` opens an Extension Development Host automatically. You can override the editor or workspace with `OPENCHAMBER_VSCODE_BIN` and `OPENCHAMBER_VSCODE_DEV_WORKSPACE`.
+
+Example: `OPENCHAMBER_VSCODE_BIN=cursor bun run vscode:dev`.
 
 ### Shared UI (`packages/ui`)
 
-No dev server — this is a source-level library consumed by other packages. During development, `bun run dev` runs type-checking in watch mode.
+No standalone app server. This is a source-level library used by Web, Desktop, and VS Code.
+
+Useful package commands:
+
+```bash
+bun run build:ui
+bun run type-check:ui
+bun run lint:ui
+```
+
+## Build And Package Commands
+
+| Command | What it does |
+|---------|--------------|
+| `bun run build` | Build all workspaces |
+| `bun run build:web` | Build only `packages/web` |
+| `bun run build:ui` | Build only `packages/ui` |
+| `bun run build:electron` | Run Electron package build script without full packaging |
+| `bun run electron:build` | Build packaged desktop app for the current OS |
+| `bun run vscode:build` | Build the VS Code extension |
+| `bun run vscode:package` | Package the VS Code extension as `.vsix` |
+| `bun run pack:web` | Create a package archive for `@openchamber/web` |
+
+## Platform Build Notes
+
+You usually build desktop installers on the target platform.
+
+macOS:
+
+```bash
+bun run electron:build
+bun run release:test:intel
+bun run release:test:arm
+```
+
+Windows:
+
+```bash
+bun run electron:build
+```
+
+Linux is supported for web/CLI development. A Linux desktop app is still planned, so Electron packaging is mainly macOS and Windows right now.
 
 ## Before Submitting
 
@@ -50,6 +104,12 @@ bun run lint         # Must pass
 bun run build        # Must succeed
 ```
 
+For docs-only changes, validation may be enough:
+
+```bash
+bun run docs:validate
+```
+
 ## Code Style
 
 - Functional React components only