The main window has no Clipboard page and no Suggestions page: two of the three things the app does are not in the sidebar

> Needs a design pass before code. `Design/` has 94 artboards and not one for either page
> proposed here, and `MainTab` is documented as "the sidebar's pages, in the approved
> design's order" (`Sources/UttrflowUX/Destination.swift:19`) — so the order is a decision
> somebody made, not an accident to be edited past. Read this as the gap being recorded,
> not as a licence to reshuffle the sidebar.

### The gap

The app ships three things a person turns on and uses — the clipboard, dictation, and
tab-to-complete. The main window has a page for one of them.

`SidebarPresenter.order` (`Sources/UttrflowUX/SidebarPresentation.swift:132`) is eleven flat
rows:

```
Home · Dictation · History · Dictionary · Corrections · Insights · Snippets · Style ·
Diagnostics · Settings · Account
```

Six of those — Dictation, History, Dictionary, Corrections, Insights, Style — are dictation's
own concerns. `MainTab` (`Sources/UttrflowUX/Destination.swift:20`) has no `clipboard` case
and no `suggestions` case, and grepping either word against `Destination.swift` and
`SidebarPresentation.swift` returns nothing.

So:

- **The clipboard has no page at all.** It exists only as the ⇧⌘V panel. Everything a person
might want to do deliberately rather than in a hurry — look through what was captured,
manage folders, review what has been masked, understand the retention window — has nowhere
to happen. The README calls the app "a native macOS clipboard manager"; the window that
opens at launch has no clipboard in it.
- **Tab-to-complete has no page.** It exists as one Settings tab
(`SettingsTab.suggestions`) and the inline panel. There is nowhere to see what it has
learned, per application, or to judge whether it is working — which matters more than
usual, because when the model is not loaded the feature is silently indistinguishable from
a feature with nothing to say (#124).

### Why it is worth recording rather than leaving

Two of the three things the app does are reachable only by knowing a keyboard shortcut or by
opening Settings. A person who opens the app and reads the sidebar top to bottom will
conclude it is a dictation app with some extra pages, which is not what it is.

The flat eleven-row list is also at the limit of what reads as a list rather than a menu, so
"add two more rows" is probably the wrong answer. Grouping the existing rows under what they
belong to is likely the real shape of this.

### What a change here would have to settle

- Whether the sidebar gains sections, and if so what the dictation-owned rows collapse into.
- What a Clipboard page contains that the ⇧⌘V panel does not, and whether it duplicates the
panel's behaviour or deliberately differs from it.
- What a Suggestions page contains beyond what the Settings tab already shows, and whether
the Settings tab then goes away or stays.
- Artboards in `Design/` for both, light and dark, in the same set as the existing pages.

### Sequencing

The Suggestions page should not ship before #124. A page whose whole job is to show what the
feature has learned is worse than nothing while the model is silently absent.

Start by reading Sources/UttrflowUX/Destination.swift:19-20 and Sources/UttrflowUX/SidebarPresentation.swift:132, then review the existing artboards in Design/. Define the sidebar structure and the distinct contents of Clipboard and Suggestions, add matching light and dark artboards, and defer Suggestions until #124 is resolved.

Written by the indexing model from the issue text.