feat(plugins): install and update Git sources (#3920)

Make every trusted Git repository directly distributable without introducing a registry or package manager. Managed checkouts retain their resolved commit, track branches explicitly, and stage validation before activation so failed updates restore the running version.

docs/data-model.md

@@ -63,6 +63,9 @@ $PASEO_HOME/
 ├── runtime/
 │   └── managed-processes/
 │       └── {recordId}.json              # Helper processes owned by Paseo; reconciled on daemon bootstrap
+├── plugins/
+│   ├── sources.json                      # Git origin, ref, commit, and managed checkout ownership
+│   └── {pluginId}/{version}/checkout/    # Source checkout for one installed Git commit
 └── push-tokens.json                     # Expo push notification tokens
 ```
 
@@ -251,6 +254,12 @@ snapshot so a mixed edit can apply its live subset and still name the paths that
 
 All fields are optional with sensible defaults.
 
+Git-managed plugins still appear as directory sources in `config.json`. This keeps the plugin
+runtime and protocol config compatible with directory-only clients. `plugins/sources.json` owns the
+Git-specific origin, tracking ref, installed commit, repository subdirectory, and checkout root.
+Paseo writes it atomically. An update creates and validates a new version directory before changing
+the configured directory path; successful activation removes the old version.
+
 ### Profile lists
 
 `terminalProfiles` and `agentProfiles` are both whole-list fields: a config patch replaces the

docs/plugins.md

@@ -1,9 +1,9 @@
-# Local plugins
+# Plugins
 
 Local plugins contribute daemon RPCs, native app surfaces, workspace panels, Command Center items,
 app themes, and composer attachment sources from one `index.ts`. Paseo executes the server contribution in a
 subprocess and evaluates the client contribution in the app runtime. Plugin code is trusted code;
-this first slice does not sandbox it.
+Paseo does not sandbox it.
 
 ## Install a directory source
 
@@ -74,8 +74,33 @@ backend code can access the daemon machine, while client contributions run insid
 
 Source changes are explicit. Run `paseo plugin reload <id>` to stop and fully tear down the old
 plugin before compiling and starting from disk. A failed reload stays failed; Paseo does not restore
-the old code. Use `enable`, `disable`, and `remove` to manage one plugin. Remove deletes only its
-configuration, never its source directory. The global `pluginsEnabled` switch remains available.
+the old code. Use `enable`, `disable`, and `remove` to manage one plugin. Removing a directory source
+never deletes it. The global `pluginsEnabled` switch remains available.
+
+## Install a Git source
+
+GitHub repositories use an `owner/repository` shorthand. Other hosts use a Git URL. An existing
+directory always wins over shorthand resolution.
+
+```bash
+paseo plugin add owner/repository
+paseo plugin add https://git.example.com/owner/repository.git
+paseo plugin add owner/monorepo --path plugins/review
+paseo plugin add owner/repository --ref main
+paseo plugin status
+paseo plugin update review
+paseo plugin update --all
+```
+
+Omitting `--ref` tracks the remote's default branch. A branch passed with `--ref` also tracks;
+tags and commits stay pinned. `status` fetches tracked refs and reports the installed and available
+commits. `update` checks out a new version, validates its manifest, compiles both bundles, and starts
+it before changing the configured path. A compilation or startup failure restores the running
+version. Removing a Git source deletes Paseo's managed checkout.
+
+Git installation does not run a package manager or install script. A distributable source plugin
+uses Paseo's host-provided modules or commits any other bundled source it needs. Native React Native
+dependencies work only when the Paseo app already ships the native module.
 
 Server contributions can write to stdout and stderr with normal Node logging. Paseo adds `[paseo]`
 entries for loading, ready, stopping, and stopped transitions. Compilation and load failures are