fix(docs): tighten onBrokenLinks to throw and fix surfaced broken links (#40102)

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

docs/developer_docs/guidelines/backend-style-guidelines.md

@@ -114,7 +114,7 @@ class CreateDashboardCommand(BaseCommand):
 
 ### Data Access Objects (DAOs)
 
-See: [DAO Style Guidelines and Best Practices](./backend/dao-style-guidelines)
+See: [DAO Style Guidelines and Best Practices](./backend/dao-style-guidelines.md)
 
 ## Testing
 

docs/developer_docs/guidelines/frontend-style-guidelines.md

@@ -29,16 +29,16 @@ This is a list of statements that describe how we do frontend development in Sup
 - We develop using TypeScript.
   - See: [SIP-36](https://github.com/apache/superset/issues/9101)
 - We use React for building components, and Redux to manage app/global state.
-  - See: [Component Style Guidelines and Best Practices](./frontend/component-style-guidelines)
+  - See: [Component Style Guidelines and Best Practices](./frontend/component-style-guidelines.md)
 - We prefer functional components to class components and use hooks for local component state.
 - We use [Ant Design](https://ant.design/) components from our component library whenever possible, only building our own custom components when it's required.
   - See: [SIP-48](https://github.com/apache/superset/issues/11283)
 - We use [@emotion](https://emotion.sh/docs/introduction) to provide styling for our components, co-locating styling within component files.
   - See: [SIP-37](https://github.com/apache/superset/issues/9145)
-  - See: [Emotion Styling Guidelines and Best Practices](./frontend/emotion-styling-guidelines)
+  - See: [Emotion Styling Guidelines and Best Practices](./frontend/emotion-styling-guidelines.md)
 - We use Jest for unit tests, React Testing Library for component tests, and Cypress for end-to-end tests.
   - See: [SIP-56](https://github.com/apache/superset/issues/11830)
-  - See: [Testing Guidelines and Best Practices](../testing/testing-guidelines)
+  - See: [Testing Guidelines and Best Practices](../testing/testing-guidelines.md)
 - We add tests for every new component or file added to the frontend.
 - We organize our repo so similar files live near each other, and tests are co-located with the files they test.
   - See: [SIP-61](https://github.com/apache/superset/issues/12098)
@@ -46,6 +46,6 @@ This is a list of statements that describe how we do frontend development in Sup
 - We use OXC (oxlint) and Prettier to automatically fix lint errors and format the code.
   - We do not debate code formatting style in PRs, instead relying on automated tooling to enforce it.
   - If there's not a linting rule, we don't have a rule!
-  - See: [Linting How-Tos](../contributing/howtos#typescript--javascript)
+  - See: [Linting How-Tos](../contributing/howtos.md#typescript--javascript)
 - We use [React Storybook](https://storybook.js.org/) to help preview/test and stabilize our components
   - A public Storybook with components from the `master` branch is available [here](https://apache-superset.github.io/superset-ui/?path=/story/*)

docs/developer_docs/guidelines/frontend/component-style-guidelines.md

@@ -31,7 +31,7 @@ This guide is intended primarily for reusable components. Whenever possible, all
 ## General Guidelines
 
 - We use [Ant Design](https://ant.design/) as our component library. Do not build a new component if Ant Design provides one but rather instead extend or customize what the library provides
-- Always style your component using Emotion and always prefer the theme variables whenever applicable. See: [Emotion Styling Guidelines and Best Practices](./emotion-styling-guidelines)
+- Always style your component using Emotion and always prefer the theme variables whenever applicable. See: [Emotion Styling Guidelines and Best Practices](./emotion-styling-guidelines.md)
 - All components should be made to be reusable whenever possible
 - All components should follow the structure and best practices as detailed below
 
@@ -53,7 +53,7 @@ superset-frontend/src/components
 
 **Storybook:** Components should come with a storybook file whenever applicable, with the following naming convention `\{ComponentName\}.stories.tsx`. More details about Storybook below
 
-**Unit and end-to-end tests:** All components should come with unit tests using Jest and React Testing Library. The file name should follow this naming convention `\{ComponentName\}.test.tsx`. Read the [Testing Guidelines and Best Practices](../../testing/testing-guidelines) for more details
+**Unit and end-to-end tests:** All components should come with unit tests using Jest and React Testing Library. The file name should follow this naming convention `\{ComponentName\}.test.tsx`. Read the [Testing Guidelines and Best Practices](../../testing/testing-guidelines.md) for more details
 
 **Reference naming:** Use `PascalCase` for React components and `camelCase` for component instances