refactor(plugins): split PluginStoreManager into mixins (#659)

* refactor(plugins): split PluginStoreManager into mixins

src/plugin_system/store_manager.py (2,977 lines) keeps the class, its
shared state, locks, the uninstall registry, directory lookup and
uninstall; its methods are split by area into:
- store_registry.py (_RegistryMixin): registry, GitHub metadata, search,
  manifest validation
- store_install.py (_InstallMixin): install paths and dependencies
- store_update.py (_UpdateMixin): updates, rollback, local git state

Pure move: all 56 members are byte-identical (checked with ast) and the
assembled class has exactly the same attributes as before (checked at
runtime). PluginStoreManager is imported from store_manager.py as before.
Tests that patched shared modules (subprocess, requests, tempfile, shutil)
through store_manager now reach them through the module whose code they
exercise; a source-text contract test reads all store_*.py modules.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* chore: annotate findings the split moved into new store modules

subprocess imports and a list-form git clone (no shell), and the config
template's placeholder token string -- existing code that Codacy reported
as new because it moved. Annotated with the repo's nosec/nosemgrep style.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* chore: annotate the default-branch git clone the split moved

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/ARCHITECTURE.md

@@ -127,7 +127,7 @@ then normal rotation.
 | Circuit breaker | [`plugin_health.py`](../src/plugin_system/plugin_health.py) (`PluginHealthTracker`: 3 consecutive failures open the circuit for 300 s) |
 | Resource metrics | [`resource_monitor.py`](../src/plugin_system/resource_monitor.py) |
 | Config schemas and defaults | [`schema_manager.py`](../src/plugin_system/schema_manager.py) |
-| Install, update, uninstall | [`store_manager.py`](../src/plugin_system/store_manager.py) (`PluginStoreManager`) |
+| Install, update, uninstall | [`store_manager.py`](../src/plugin_system/store_manager.py) (`PluginStoreManager`), with its methods split across [`store_registry.py`](../src/plugin_system/store_registry.py) (registry, GitHub), [`store_install.py`](../src/plugin_system/store_install.py) and [`store_update.py`](../src/plugin_system/store_update.py) |
 | Core-version gate | [`compatibility.py`](../src/plugin_system/compatibility.py) |
 
 Discovery scans only `plugin_system.plugins_directory` (default

docs/CONFIG_REFERENCE.md

@@ -180,5 +180,5 @@ See [PLUGIN_CONFIG_CORE_PROPERTIES.md](PLUGIN_CONFIG_CORE_PROPERTIES.md).
 
 | Key | Meaning |
 |---|---|
-| `github.api_token` | Optional GitHub token the Plugin Store uses to avoid API rate limits (`src/plugin_system/store_manager.py`) |
+| `github.api_token` | Optional GitHub token the Plugin Store uses to avoid API rate limits (`src/plugin_system/store_registry.py`) |
 | `<plugin-id>.*` | Secrets a plugin declares with `"x-secret": true` in its config schema; merged into that plugin's config at load time |

docs/PLUGIN_API_REFERENCE.md

@@ -26,7 +26,7 @@ fields:
 | Check | Fields | What happens when one is missing |
 |---|---|---|
 | JSON schema, [`schema/manifest_schema.json`](../schema/manifest_schema.json) | `id`, `name`, `version`, `author`, `entry_point`, `class_name`, `compatible_versions` | Install from URL logs a warning (`PluginStoreManager._validate_manifest_schema()`); nothing is refused |
-| Plugin Store install, [`src/plugin_system/store_manager.py`](../src/plugin_system/store_manager.py) | `id`, `name`, `class_name`, `display_modes` | Install is refused. A registry install first tries to detect a missing `class_name` from the entry-point file |
+| Plugin Store install, [`src/plugin_system/store_install.py`](../src/plugin_system/store_install.py) | `id`, `name`, `class_name`, `display_modes` | Install is refused. A registry install first tries to detect a missing `class_name` from the entry-point file |
 | Plugin loader, [`src/plugin_system/plugin_loader.py`](../src/plugin_system/plugin_loader.py) | `class_name` | The plugin fails to load |
 
 Defaults and other uses:

docs/PLUGIN_CONFIGURATION_GUIDE.md

@@ -202,7 +202,7 @@ plugin-repos/
 ```
 
 The Plugin Store refuses a manifest that lacks any of `id`, `name`,
-`class_name` or `display_modes` (`store_manager.py`); the loader itself
+`class_name` or `display_modes` (`store_install.py`); the loader itself
 needs `class_name`. `version` is not required, but the store compares it
 with the registry's `latest_version` to offer updates, so set it.
 `entry_point` defaults to `manager.py` if omitted. The config schema is not

docs/PLUGIN_DEPENDENCY_GUIDE.md

@@ -25,7 +25,7 @@ which runs as root.** Anything installed only into another user's
 The web interface is not root, so it installs through a narrow sudo helper:
 
 1. `PluginStoreManager._install_dependencies()`
-   (`src/plugin_system/store_manager.py`) calls
+   (`src/plugin_system/store_install.py`) calls
    `install_requirements_file()` (`src/common/permission_utils.py`).
 2. That runs `sudo -n bash scripts/fix_perms/safe_pip_install.sh <plugin>/requirements.txt`.
    The helper checks the path is the project's own `requirements.txt` or a
@@ -154,7 +154,7 @@ For more, see the [Plugin Dependency Troubleshooting Guide](PLUGIN_DEPENDENCY_TR
 ## Files to Reference
 
 - Service units: `systemd/ledmatrix.service`, `systemd/ledmatrix-web.service`
-- Store installs: `src/plugin_system/store_manager.py` (`_install_dependencies`)
+- Store installs: `src/plugin_system/store_install.py` (`_install_dependencies`)
 - Root install helper: `src/common/permission_utils.py` (`install_requirements_file`), `scripts/fix_perms/safe_pip_install.sh`
 - Load-time installs: `src/plugin_system/plugin_loader.py` (`install_dependencies`)
 - Sudo rules: `scripts/install/lib_sudoers.sh` (written by `first_time_install.sh`