feat(docs): Populate Developer Portal with comprehensive documentation framework (#35217)

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

docs/developer_portal/extensions/interacting-with-host.md

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+---
+title: Interacting with the Host
+sidebar_position: 6
+---
+
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+KIND, either express or implied.  See the License for the
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+
+# Interacting with the Host
+
+Extensions interact with Superset through well-defined, versioned APIs provided by the `@apache-superset/core` (frontend) and `apache-superset-core` (backend) packages. These APIs are designed to be stable, discoverable, and consistent for both built-in and external extensions.
+
+**Frontend APIs** (via `@apache-superset/core)`:
+
+The frontend extension APIs in Superset are organized into logical namespaces such as `authentication`, `commands`, `extensions`, `sqlLab`, and others. Each namespace groups related functionality, making it easy for extension authors to discover and use the APIs relevant to their needs. For example, the `sqlLab` namespace provides events and methods specific to SQL Lab, allowing extensions to react to user actions and interact with the SQL Lab environment:
+
+``` typescript
+export const getCurrentTab: () => Tab | undefined;
+
+export const getDatabases: () => Database[];
+
+export const getTabs: () => Tab[];
+
+export const onDidChangeEditorContent: Event<string>;
+
+export const onDidClosePanel: Event<Panel>;
+
+export const onDidChangeActivePanel: Event<Panel>;
+
+export const onDidChangeTabTitle: Event<string>;
+
+export const onDidQueryRun: Event<Editor>;
+
+export const onDidQueryStop: Event<Editor>;
+```
+
+The following code demonstrates more examples of the existing frontend APIs:
+
+``` typescript
+import { core, commands, sqlLab, authentication, Button } from '@apache-superset/core';
+import MyPanel from './MyPanel';
+
+export function activate(context) {
+  // Register a new panel (view) in SQL Lab and use shared UI components in your extension's React code
+  const panelDisposable = core.registerView('my_extension.panel', <MyPanel><Button/></MyPanel>);
+
+  // Register a custom command
+  const commandDisposable = commands.registerCommand('my_extension.copy_query', {
+    title: 'Copy Query',
+    execute: () => {
+      // Command logic here
+    },
+  });
+
+  // Listen for query run events in SQL Lab
+  const eventDisposable = sqlLab.onDidQueryRun(editor => {
+    // Handle query execution event
+  });
+
+  // Access a CSRF token for secure API requests
+  authentication.getCSRFToken().then(token => {
+    // Use token as needed
+  });
+
+  // Add all disposables for automatic cleanup on deactivation
+  context.subscriptions.push(panelDisposable, commandDisposable, eventDisposable);
+}
+```
+
+**Backend APIs** (via `apache-superset-core`):
+
+Backend APIs follow a similar pattern, providing access to Superset's models, sessions, and query capabilities. Extensions can register REST API endpoints, access the metadata database, and interact with Superset's core functionality.
+
+Extension endpoints are registered under a dedicated `/extensions` namespace to avoid conflicting with built-in endpoints and also because they don't share the same version constraints. By grouping all extension endpoints under `/extensions`, Superset establishes a clear boundary between core and extension functionality, making it easier to manage, document, and secure both types of APIs.
+
+``` python
+from superset_core.api import rest_api, models, query
+from .api import DatasetReferencesAPI
+
+# Register a new extension REST API
+rest_api.add_extension_api(DatasetReferencesAPI)
+
+# Access Superset models with simple queries that filter out entities that
+# the user doesn't have access to
+databases = models.get_databases(id=database_id)
+if not databases:
+    return self.response_404()
+
+database = databases[0]
+
+# Perform complex queries using SQLAlchemy BaseQuery, also filtering
+# out inaccessible entities
+session = models.get_session()
+db_model = models.get_database_model())
+database_query = session.query(db_model.database_name.ilike("%abc%")
+databases_containing_abc = models.get_databases(query)
+
+# Bypass security model for highly custom use cases
+session = models.get_session()
+db_model = models.get_database_model())
+all_databases_containg_abc = session.query(db_model.database_name.ilike("%abc%").all()
+```
+
+In the future, we plan to expand the backend APIs to support configuring security models, database engines, SQL Alchemy dialects, etc.