Model downloader dialog (#569)

* API core for model downloader

* initial basic dialog for missing models

* app.ts handling for missing models

* don't explode if getModels is a 404

* actually track downloads in progress

* overall pile of improvements to the missing models view

* minor fixes

* add setting to disable missing models warning

* temporarily remove 'models' entry from default graph

to avoid missing model dialog causing issues. Also because ckpt autodownloading shouldn't be allowed

* swap the url to a title

* add model directory to display

* match settingStore commit

* check setting before scanning models list

ie avoid redundant calcs when setting is disabled anyway

tests-ui/utils/setup.ts

@@ -73,6 +73,7 @@ export function mockApi(config: APIConfig = {}) {
       userConfig.users[username + '!'] = username
       return { status: 200, json: () => username + '!' }
     }),
+    getModels: jest.fn(() => []),
     getUserConfig: jest.fn(
       () => userConfig ?? { storage: 'browser', migrated: false }
     ),