docs: rename package discovery to feature discovery and reduce duplication

Rename "package discovery" to "feature discovery" across all plugin
READMEs and docs to match the established terminology. Slim down the
Feature Discovery section in the architecture docs to avoid duplicating
the configuration details now covered in the installing plugins page.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor
Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor

docs/frontend-system/building-apps/01-index.md

@@ -65,7 +65,7 @@ Linking routes from different plugins requires this configuration. You can do th
 
 ### Install plugins
 
-Plugins are typically installed by adding them as dependencies of your app package and relying on package discovery to automatically detect them. For details on how this works, including how to manually install plugins or control which packages are discovered, see [Installing Plugins](./05-installing-plugins.md).
+Plugins are typically installed by adding them as dependencies of your app package and relying on feature discovery to automatically detect them. For details on how this works, including how to manually install plugins or control which packages are discovered, see [Installing Plugins](./05-installing-plugins.md).
 
 ### Configure extensions individually
 
@@ -79,7 +79,7 @@ Previously you would customize the application routes, components, apis, sidebar
 
 ### Install features manually
 
-Most plugins are installed automatically through [package discovery](./05-installing-plugins.md#package-discovery). Manual installation is needed if your packages are not discovered automatically, either because you are not using `@backstage/cli` to build your application or because the features are defined in local modules in the app package. In order to manually install a feature, you must import it and pass it to the `createApp` function:
+Most plugins are installed automatically through [feature discovery](./05-installing-plugins.md#feature-discovery). Manual installation is needed if your packages are not discovered automatically, either because you are not using `@backstage/cli` to build your application or because the features are defined in local modules in the app package. In order to manually install a feature, you must import it and pass it to the `createApp` function:
 
 ```tsx title="packages/app/src/App.tsx"
 import { createApp } from '@backstage/frontend-defaults';

docs/frontend-system/building-apps/05-installing-plugins.md

@@ -15,11 +15,11 @@ To install a plugin, add it as a dependency to your app package. For example, to
 yarn --cwd packages/app add @backstage/plugin-catalog
 ```
 
-If your app is set up with [package discovery](#package-discovery), the plugin will be automatically detected and installed in the app. No additional code changes are needed.
+If your app is set up with [feature discovery](#feature-discovery), the plugin will be automatically detected and installed in the app. No additional code changes are needed.
 
-## Package discovery
+## Feature discovery
 
-Package discovery lets the app automatically discover and install plugins from the dependencies of your app package. This is enabled by setting `app.packages` to `all` in your `app-config.yaml`:
+Feature discovery lets the app automatically discover and install plugins from the dependencies of your app package. This is enabled by setting `app.packages` to `all` in your `app-config.yaml`:
 
 ```yaml title="app-config.yaml"
 app:
@@ -43,13 +43,13 @@ app:
       - '@backstage/plugin-catalog'
 ```
 
-Package discovery requires that your app is built using the `@backstage/cli`, which is the default for all Backstage apps. Note that you do not need to exclude packages that you also install manually in code, since plugin instances are deduplicated by the app.
+Feature discovery requires that your app is built using the `@backstage/cli`, which is the default for all Backstage apps. Note that you do not need to exclude packages that you also install manually in code, since plugin instances are deduplicated by the app.
 
-For more details on how package discovery works under the hood, see the [Feature Discovery](../architecture/10-app.md#feature-discovery) architecture documentation.
+For more details on how feature discovery works under the hood, see the [Feature Discovery](../architecture/10-app.md#feature-discovery) architecture documentation.
 
 ## Manual installation
 
-If your app does not have [package discovery](#package-discovery) enabled, or if you need more control over the plugin installation, you can install plugins manually. This is done by importing the plugin and passing it to `createApp`:
+If your app does not have [feature discovery](#feature-discovery) enabled, or if you need more control over the plugin installation, you can install plugins manually. This is done by importing the plugin and passing it to `createApp`:
 
 ```tsx title="packages/app/src/App.tsx"
 import { createApp } from '@backstage/frontend-defaults';
@@ -62,7 +62,7 @@ const app = createApp({
 export default app.createRoot();
 ```
 
-Manual installation may also be necessary if you need to control the ordering of plugins, for example when customizing route priorities. Since manually installed plugins are deduplicated against automatically discovered ones, you can safely install a plugin both manually and through package discovery without causing conflicts.
+Manual installation may also be necessary if you need to control the ordering of plugins, for example when customizing route priorities. Since manually installed plugins are deduplicated against automatically discovered ones, you can safely install a plugin both manually and through feature discovery without causing conflicts.
 
 If you need to use a 3rd-party plugin that does not yet support the new frontend system, you can use the conversion utilities from `@backstage/core-compat-api` to wrap it. See [Converting 3rd-party Plugins](./06-plugin-conversion.md) for details.