[core/plugins] Add PluginLoader, SubmitterProvider, and config.json name/version resolution

AGENTS.md

@@ -57,7 +57,7 @@ A few distinctions are easy to confuse. Keep them straight before changing engin
 * **Graph = DAG of attributes.** A **`Graph`** (`meshroom/core/graph.py`) holds nodes connected by **`Edge`**s that link one node's *output* attribute to another node's *input* attribute. A connected input reads its value from upstream; the graph is a DAG and defines evaluation order. Each node computes a content-based **UID** (hash of its inputs) so unchanged nodes can be cached and skipped on recompute.
 * **Execution = chunks.** Work is split into **`NodeChunk`**s for parallelism (driven by the descriptor's `size`/`parallelization`). `desc.Node` subclasses implement **`processChunk(chunk)`** in Python; `desc.CommandLineNode` builds a command line from its `commandLine` template plus the chunk's range and runs the external binary. **`TaskManager`** (`meshroom/core/taskManager.py`) orchestrates execution — either **locally** (`compute`) or by **submitting** to a render farm (`submit`) via `meshroom/submitters/`.
 * **Persistence.** Graphs are saved as **`.mg`** JSON files (`meshroom/core/graphIO.py`): a versioned `header` plus a `graph` payload. On load, `nodeFactory` reconciles descriptor changes so old projects still open — a node that no longer matches its current descriptor becomes a **`CompatibilityNode`** instead of failing. Pipeline **templates** are just `.mg` files registered at startup.
-* **Discovery.** Node types and pipeline templates are loaded at import time (`meshroom/core/__init__.py`, `meshroom/core/plugins.py`) from the built-in `meshroom/nodes/` plus any plugin/template paths (see [INSTALL_PLUGINS.md](INSTALL_PLUGINS.md)).
+* **Discovery.** Node types and pipeline templates are loaded at import time (`meshroom/core/__init__.py`, `meshroom/core/plugins/`) from the built-in `meshroom/nodes/` plus any plugin/template paths (see [INSTALL_PLUGINS.md](INSTALL_PLUGINS.md)).
 * **UI bridge.** The engine is Qt-agnostic: `meshroom/common/` selects either a Qt or a headless backend for `BaseObject`, so the core runs without a UI. The `meshroom/ui/*.py` layer wraps it for Qt — `app.py` (application/entry), `graph.py` (a `UIGraph` exposing the core `Graph` as Qt models + async compute), `commands.py` (undo/redo command stack), `scene.py`. QML in `meshroom/ui/qml/` binds to these.
 
 ## Development & Verification

INSTALL_PLUGINS.md

@@ -5,7 +5,7 @@ Plugins are collections of nodes and templates with their own dependencies. Plug
 ## Required Structure
 
 - **Meshroom folder**: All plugin nodes and templates must be placed within a `./meshroom/` directory
-- **Configuration file (optional)**: `./meshroom/config.json` file allows to define custom environment variables for the plugin  
+- **Configuration file (optional)**: `./meshroom/config.json` file allows to define the plugin's name, version and custom environment variables
 - **Virtual environment (optional)**: If you have specific dependencies, you can create a virtual environment named "venv" in a folder and this Python will be used when computing the node.
 
 ## Example Structure
@@ -18,8 +18,7 @@ For a plugin named "customPlugin", Meshroom expects this layout:
 │   │   │   ├── __init__.py      # Required to be a python module
 │   │   │   ├── NodeA.py
 │   │   │   ├── NodeB.py
-│   │   ├── customNodes2/        # Another set of nodes if needed
-│   │   │   ├── __init__.py
+│   │   ├── customNodes2/        # Another set of standalone nodes
 │   │   │   ├── NodeC.py
 │   │   │   ├── NodeD.py
 │   │   ├── customTemplate1.mg   # Ready-to-use pipeline templates
@@ -29,6 +28,28 @@ For a plugin named "customPlugin", Meshroom expects this layout:
 │   └── ...                      # Custom code (any structure)
 ```
 
+## Configuration File
+
+`config.json` can be written in two formats:
+
+- A plain list of environment variable entries:
+  ```json
+  [
+      { "key": "MY_VAR", "type": "string", "value": "myValue" },
+      { "key": "MY_PATH", "type": "path", "value": "relativeOrAbsolutePath" }
+  ]
+  ```
+- An object with optional `name`, `version`, and `env` keys, `env` using the same entry format as above:
+  ```json
+  {
+      "name": "customPlugin",
+      "version": "1.0.0",
+      "env": [
+          { "key": "MY_VAR", "type": "string", "value": "myValue" }
+      ]
+  }
+  ```
+
 ## Loading the Plugin
 
 The "customPlugin" will be loaded automatically when Meshroom starts by setting the `MESHROOM_PLUGINS_PATH` environment variable: