refactor: migrate remaining Vue components to <script setup> (#38752)

Migrates the last four Options API components, so all 20 `.vue` files
now use `<script setup>`, and disables the Vue Options API runtime. This
will enable optimizations like Vue Vapor mode in the future.

Bug fixes done while migrating and testing:

- Branch selector: arrowing onto "Create branch …" threw a `TypeError`,
and Enter on it did nothing
- Dashboard: the search term was not escaped, so `&` injected query
parameters and `#` truncated the request
- Dashboard: an unknown `repo-search-filter` threw, and names like
`constructor` leaked `Object.prototype` members into the request
- Dashboard: an unknown archived/private filter rendered `function
Object() { [native code] }` as a checkbox tooltip
- Dashboard: removed a dropdown init that always ran against a
not-yet-rendered element
- Branch selector: the `document.body` click listener was never removed
on unmount
- Contributors: the chart plugin relied on an undeclared chart.js field
- Contributors: `contributorsStats` was mutated behind a `shallowRef`,
so future readers would not update
- Removed template attributes and pageData keys that no component had
read for years

---------

Signed-off-by: silverwind <me@silverwind.io>

vitest.config.ts

@@ -1,6 +1,5 @@
 import {defineConfig} from 'vitest/config';
-import vuePlugin from '@vitejs/plugin-vue';
-import {stringPlugin} from 'vite-string-plugin';
+import {sharedPlugins, vueDefines} from './tools/shared.ts';
 
 export default defineConfig({
   test: {
@@ -21,8 +20,6 @@ export default defineConfig({
       concurrent: true,
     },
   },
-  plugins: [
-    stringPlugin(),
-    vuePlugin(),
-  ],
+  define: vueDefines,
+  plugins: sharedPlugins(),
 });