docs: make SDK README PyPI friendly

packages/setuav-studio-sdk/README.md

@@ -1,29 +1,77 @@
 # Setuav Studio SDK
 
-This package defines the Python contracts used by third-party Setuav Studio
-plugins. The source and API reference are kept together for versioned releases.
+The Setuav Studio SDK defines the public Python contracts used by third-party
+plugins. It provides the plugin lifecycle, `StudioAPI`, contribution
+descriptors, and provider callback types without exposing application
+implementation details.
 
-## Developer documentation
-
-From this directory:
+## Installation
 
 ```bash
-doxygen Doxyfile
+pip install setuav-studio-sdk
+```
+
+The SDK supports Python 3.11 and newer.
+
+## Plugin lifecycle
+
+A plugin exposes a stable reverse-domain ID, registers its contributions in
+`activate`, and removes them in `deactivate`:
+
+```python
+from PySide6.QtWidgets import QLabel
+
+from setuav_studio_sdk import PanelContribution, StudioAPI
+
+
+class HelloPlugin:
+    id = "com.example.hello"
+    priority = 100
+
+    def activate(self, api: StudioAPI) -> None:
+        api.add_panel(
+            PanelContribution(
+                id="com.example.hello.panel",
+                title="Hello Plugin",
+                factory=lambda: QLabel("Hello from a Setuav Studio plugin"),
+            )
+        )
+
+    def deactivate(self, api: StudioAPI) -> None:
+        api.remove_panel("com.example.hello.panel")
 ```
 
-Open `docs/html/index.html` in a browser.
+Plugins are discovered through the `setuav_studio.plugins` Python entry-point
+group. Contribution and entry-point IDs must be unique; use a reverse-domain
+prefix owned by your project.
 
-The generated reference documents only public SDK modules. Application
-implementation modules are deliberately excluded.
+Declare the plugin entry point in `pyproject.toml`:
+
+```toml
+[project.entry-points."setuav_studio.plugins"]
+"com.example.hello" = "my_plugin.plugin:HelloPlugin"
+```
 
-## Example plugin
+## API reference
 
-The [`packages/example-plugin`](../example-plugin) project shows the
-smallest installable plugin: it declares the SDK dependency, publishes an
-entry point, and cleans up its workspace and panel during deactivation.
+Read the [online SDK API reference](https://setuav.github.io/Studio/developer/sdk-api-reference/)
+for the complete public contract documentation.
 
-Run the SDK and example-plugin tests from the repository root:
+The [example plugin](https://github.com/Setuav/Studio/tree/main/packages/example-plugin)
+contains package metadata, an entry point, lifecycle implementation, and
+tests that can be used as a starting point for a new plugin.
+
+## Development
+
+To regenerate the API reference or run the contract tests, clone the
+[Setuav Studio repository](https://github.com/Setuav/Studio) and run these
+commands from its root:
 
 ```bash
-python scripts/sdk_contract_tests.py
+cd packages/setuav-studio-sdk
+doxygen Doxyfile
+cd ../..
+uv run --locked python scripts/sdk_contract_tests.py
 ```
+
+The generated reference documents only public `setuav_studio_sdk` modules.