delete two unreferenced components from another codebase

MarkdownEditor and ui/start-confetti-button had no importers anywhere in the repo
and both carried a different product's content: MarkdownEditor hardcoded
https://app.pertento.ai/logo.png with alt="Pertento", and start-confetti-button
spoke about 'the experiment' and 'Draft/Created' statuses.

Translating either would have put feature words into ui.*, which D6 forbids —
a shared namespace may not name a feature.

todo/inputs-outside-forms named MarkdownEditor as deliberately-unwrapped, so that
entry is updated rather than left pointing at a deleted file.

todo/inputs-outside-forms/_index.md

@@ -49,9 +49,10 @@ handling.
 - `Dashboards/DashboardPreview`'s `NamePanel` (name + description) has its submit button in a
   _different_, independently-mounted panel (`CreatePanel`) elsewhere in the workspace layout tree — a
   `<form>` can't span two panels without restructuring the wizard.
-- `ColorPicker` and `MarkdownEditor` have zero call sites anywhere in the repo right now; both are
-  shaped to be embedded in a future caller's own form (uncontrolled inputs with `name` attributes, or a
-  plain controlled textarea with no submit of its own), so there's nothing to wrap yet.
+- `ColorPicker` has zero call sites anywhere in the repo right now; it is shaped to be embedded in a
+  future caller's own form (uncontrolled inputs with `name` attributes), so there's nothing to wrap yet.
+  `MarkdownEditor` was named here too and was deleted on 2026-08-23 during the localization pass — it
+  had no call sites and hardcoded another product's logo URL.
 - `widgets/Weather`'s `LocationSetup` is a live autocomplete with several result rows and no single
   obvious Enter target (which of N matches?).