docs: fix broken links, missing sidebar entries, and restore lost content

- Replace all /developer_portal/ links with /developer-docs/ in index.md
- Fix non-existent extension-project-structure references
- Fix sidebar links using old /docs/ paths (/user-docs/ instead)
- Add missing extension-points/editors and pkg-resources-migration to sidebar
- Restore Kubernetes debugging section lost during howtos migration
- Restore pkg-resources-migration.md deleted during bifurcation
- Fix versioned docs quickstart.mdx missing version prefix
- Update stale developer_portal references in README, DOCS_CLAUDE, intro.md
- Fix broken creating-viz-plugins link in intro.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/developer_docs/contributing/development-setup.md

@@ -1012,7 +1012,7 @@ When contributing new React components to Superset, please try to add a Story al
 
 The topic of authoring new plugins, whether you'd like to contribute
 it back or not has been well documented in the
-[the documentation](https://superset.apache.org/docs/contributing/creating-viz-plugins), and in [this blog post](https://preset.io/blog/building-custom-viz-plugins-in-superset-v2).
+[the documentation](/developer-docs/contributing/howtos#creating-visualization-plugins), and in [this blog post](https://preset.io/blog/building-custom-viz-plugins-in-superset-v2).
 
 To contribute a plugin to Superset, your plugin must meet the following criteria:
 

docs/developer_docs/contributing/howtos.md

@@ -256,6 +256,30 @@ For debugging the Flask backend:
 
 2. Set breakpoints and press F5 to debug
 
+### Debugging Server App in Kubernetes Environment
+
+To debug Flask running in a POD inside a kubernetes cluster, you'll need to make sure the pod runs as root and is granted the `SYS_PTRACE` capability. These settings should not be used in production environments.
+
+```yaml
+  securityContext:
+    capabilities:
+      add: ["SYS_PTRACE"]
+```
+
+See [set capabilities for a container](https://kubernetes.io/docs/tasks/configure-pod-container/security-context/#set-capabilities-for-a-container) for more details.
+
+Once the pod is running as root and has the `SYS_PTRACE` capability it will be able to debug the Flask app.
+
+You can follow the same instructions as in `docker compose`. Enter the pod and install the required library and packages: gdb, netstat and debugpy.
+
+Often in a Kubernetes environment nodes are not addressable from outside the cluster. VSCode will thus be unable to remotely connect to port 5678 on a Kubernetes node. In order to do this you need to create a tunnel that port forwards 5678 to your local machine.
+
+```bash
+kubectl port-forward  pod/superset-<some random id> 5678:5678
+```
+
+You can now launch your VSCode debugger with the same config as above. VSCode will connect to 127.0.0.1:5678 which is forwarded by kubectl to your remote kubernetes POD.
+
 ### Storybook
 
 See the dedicated [Storybook documentation](../testing/storybook) for information on running Storybook locally and adding new stories.

docs/developer_docs/contributing/pkg-resources-migration.md

@@ -0,0 +1,94 @@
+---
+title: pkg_resources Migration Guide
+sidebar_position: 9
+---
+
+<!--
+Licensed to the Apache Software Foundation (ASF) under one
+or more contributor license agreements.  See the NOTICE file
+distributed with this work for additional information
+regarding copyright ownership.  The ASF licenses this file
+to you under the Apache License, Version 2.0 (the
+"License"); you may not use this file except in compliance
+with the License.  You may obtain a copy of the License at
+
+  http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing,
+software distributed under the License is distributed on an
+"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+KIND, either express or implied.  See the License for the
+specific language governing permissions and limitations
+under the License.
+-->
+
+# pkg_resources Deprecation and Migration Guide
+
+## Background
+
+As of setuptools 81.0.0, the `pkg_resources` API is deprecated and will be removed. This affects several packages in the Python ecosystem.
+
+## Current Status
+
+### Superset Codebase
+
+The Superset codebase has already migrated away from `pkg_resources` to the modern `importlib.metadata` API:
+
+- `superset/db_engine_specs/__init__.py` - Uses `from importlib.metadata import entry_points`
+- All entry point loading uses the modern API
+
+### Production Dependencies
+
+Some third-party dependencies may still use `pkg_resources`. Monitor your dependency tree for packages that haven't migrated yet.
+
+## Migration Path
+
+### Short-term Solution
+
+Pin setuptools to version 80.x to prevent breaking changes:
+
+```python
+# requirements/base.in
+setuptools<81
+```
+
+This prevents the removal of `pkg_resources` while dependent packages are updated.
+
+### Long-term Solution
+
+Update all dependencies to use `importlib.metadata` instead of `pkg_resources`:
+
+#### Migration Example
+
+**Old (deprecated):**
+```python
+import pkg_resources
+
+version = pkg_resources.get_distribution("package_name").version
+entry_points = pkg_resources.iter_entry_points("group_name")
+```
+
+**New (recommended):**
+```python
+from importlib.metadata import version, entry_points
+
+pkg_version = version("package_name")
+eps = entry_points(group="group_name")
+```
+
+## Action Items
+
+### For Superset Maintainers
+1. The Superset codebase already uses `importlib.metadata`
+2. Monitor third-party dependencies for updates
+3. Update setuptools pin once the ecosystem is ready
+
+### For Extension Developers
+1. **Update your packages** to use `importlib.metadata` instead of `pkg_resources`
+2. **Test with setuptools >= 81.0.0** once all packages are migrated
+
+## References
+
+- [setuptools pkg_resources deprecation notice](https://setuptools.pypa.io/en/latest/pkg_resources.html)
+- [importlib.metadata documentation](https://docs.python.org/3/library/importlib.metadata.html)
+- [Migration guide](https://setuptools.pypa.io/en/latest/deprecated/pkg_resources.html)

docs/developer_docs/contributing/resources.md

@@ -110,7 +110,7 @@ flowchart TD
 
 ## Entity-Relationship Diagram
 
-For the full interactive Entity-Relationship Diagram, please visit the [main documentation](https://superset.apache.org/docs/contributing/resources).
+For the full interactive Entity-Relationship Diagram, please visit the [developer documentation](/developer-docs/contributing/resources).
 
 You can also [download the .svg](https://github.com/apache/superset/tree/master/docs/static/img/erd.svg) directly from GitHub.
 
@@ -119,7 +119,7 @@ You can also [download the .svg](https://github.com/apache/superset/tree/master/
 ### Official Documentation
 - [Apache Superset Documentation](https://superset.apache.org/docs/intro)
 - [API Documentation](https://superset.apache.org/docs/api)
-- [Configuration Guide](https://superset.apache.org/docs/installation/configuring-superset)
+- [Configuration Guide](https://superset.apache.org/admin-docs/configuration/configuring-superset)
 
 ### Community Resources
 - [Apache Superset Blog](https://preset.io/blog/)