chore(selenium-devtools-py): fold the pending notes into the first release

packages/selenium-devtools-py/CHANGELOG.md

@@ -24,6 +24,13 @@ backend and UI as the JavaScript adapters over the language-neutral
 - **pytest plugin** — auto-discovered, opt-in per run (`--devtools`,
   `--devtools-trace`), per project (`[tool.pytest.ini_options]`) or per shell
   (`DEVTOOLS_ENABLE`). Installing it never changes how an existing suite behaves.
+- **`selenium-devtools install-backend`** — puts the Node backend on disk once,
+  so a run starts a server it already has. Without it a run still works: the
+  backend is fetched with `npx` on first use, at a registry round trip per run.
+  Where that fetch fails — a proxy withholding a newly published version, say —
+  the adapter warns as the run starts and your tests then run *without capture*,
+  passing but empty, which is a worse thing to discover than an install command
+  that failed and said why.
 - Ships `py.typed`, so the annotations already on the public API reach a
   consumer's type checker instead of resolving to `Any`.
 - Requires Python 3.10+, `selenium>=4.44`, and Node.js 18+ on PATH for the