implement warnings section for internal BiDi reference (#2659)

Author: titusfortner

website_and_docs/content/documentation/warnings/_index.en.md

@@ -0,0 +1,10 @@
+---
+title: "Warnings"
+linkTitle: "Warnings"
+weight: 15
+description: >
+    Explanations for the diagnostics, annotations, and IDE warnings Selenium surfaces.
+---
+
+Selenium marks some APIs so your IDE or compiler can warn you about how they're meant to
+be used. These pages explain what each warning means and what to use instead.

website_and_docs/content/documentation/warnings/bidi-implementation.en.md

@@ -0,0 +1,38 @@
+---
+title: "BiDi implementation API is internal"
+linkTitle: "BiDi implementation API"
+weight: 1
+aliases:
+        [
+          "/documentation/warnings/SELENIUM001/"
+        ]
+description: >
+    Why Selenium's low-level BiDi implementation classes are marked internal,
+    and what to use instead.
+---
+
+If your IDE strikes through a Selenium BiDi class or method, shows an "Internal API"
+tooltip, or (in .NET) emits a compiler warning, you've reached one of Selenium's
+**internal BiDi implementation APIs**.
+
+These are the low-level classes that map directly onto the BiDi (and CDP) wire protocol,
+under namespaces like `org.openqa.selenium.bidi.*` (Java), `OpenQA.Selenium.BiDi.*`
+(.NET), `selenium.webdriver.common.bidi.*` (Python), and `Selenium::WebDriver::BiDi::*`
+(Ruby). They are public only because the higher-level features need them.
+
+## Why they are marked internal
+
+The goal is for the high-level APIs to cover everything you need, so you never have to
+reach for these low-level classes directly. They are marked internal to steer you toward
+those high-level APIs — but they remain available as an escape hatch if you have a use
+case the high-level APIs don't yet cover.
+
+## What to use instead
+
+Use the high-level BiDi APIs:
+* [network](/documentation/webdriver/bidi/network/)
+* [script](/documentation/webdriver/bidi/script/)
+
+If your use case is only possible through the internal classes, please
+[open an issue](https://github.com/SeleniumHQ/selenium/issues) so the high-level API can cover it.
+