Move every browser test to the shared wait helpers #435

Context

Browser tests wait for the SPA by polling from the page with $page->script(...), because Pest assertions check only once and sleep() starves the server that serves the page. Until now the AGENTS.md rule told each file to copy that polling loop under a file-unique name. The result:

• 200 local waitFor* functions in 96 files under tests/Browser, nearly all the same loop under another name (waitForWelcomeTestId, waitForSidebarTestId, waitForWebhookShowTestId, …);
• 196 waits that write document.querySelector('[data-testid=…]') inline.

#434 added shared helpers to tests/Pest.php, migrated ComposerUnsavedChangesTest.php and ComposerChannelSettingsTest.php, and changed the AGENTS.md rule: every wait goes through those helpers, and no new per-file waitFor* helper may be added.

Every helper takes a CSS selector where @name stands for [data-testid="name"] anywhere in it, as in $page->click('@name').

To do

• Replace every local waitFor* function with the shared helpers and delete the local copies. Helpers that only wrap one condition with a domain name (for example waitForChannelSettingsClosedMenu) may stay, built on waitForCondition.
• Rewrite every inline document.querySelector(...) wait with the selector helpers above. Split A && B conditions into one wait each only when both end states persist.
• Add a shared helper for a pattern that repeats and the helpers cannot express yet. Do not inline it.
• Drop "predate this rule" from the AGENTS.md Browser Tests section once no file has its own helper.
• Run the full browser suite in the three CI shards (./vendor/bin/pest tests/Browser --compact --parallel --processes=3 --shard=N/3).

Pure test refactor: no app code changes. Split it into several PRs by area if that keeps review easy.

Files with their own waitFor* helpers

• tests/Browser/ApiKeyCreateDialogTest.php
• tests/Browser/AuthLanguageSwitcherTest.php
• tests/Browser/AuthStandardFormTest.php
• tests/Browser/AuthTitlesTest.php
• tests/Browser/BillingPageTest.php
• tests/Browser/BillingProcessingTest.php
• tests/Browser/CalendarPageTest.php
• tests/Browser/ChangelogTest.php
• tests/Browser/ChannelGridTest.php
• tests/Browser/ChannelInsightsFiltersTest.php
• tests/Browser/ChannelInsightsTest.php
• tests/Browser/ChannelMediaIssueTest.php
• tests/Browser/ChannelMetricsCardTest.php
• tests/Browser/ChannelPostingGoalTest.php
• tests/Browser/ChannelReorderTest.php
• tests/Browser/ChannelSettingsPageTest.php
• tests/Browser/ChannelsSettingsTest.php
• tests/Browser/CommandPaletteTest.php
• tests/Browser/ComposerApprovalTest.php
• tests/Browser/ComposerAutosaveTest.php
• tests/Browser/ComposerCanvaMenuTest.php
• tests/Browser/ComposerChannelSettingsTest.php
• tests/Browser/ComposerEditInCanvaTest.php
• tests/Browser/ComposerGooglePhotosTest.php
• tests/Browser/ComposerMediaSourcesTest.php
• tests/Browser/ComposerMediaTrayTest.php
• tests/Browser/ComposerMobileTest.php
• tests/Browser/ComposerNetworkCardsTest.php
• tests/Browser/ComposerPreviewTest.php
• tests/Browser/ComposerQueueTest.php
• tests/Browser/ComposerSharedDataTest.php
• tests/Browser/ComposerSingleChannelTest.php
• tests/Browser/ComposerTemplatesTest.php
• tests/Browser/ComposerTimezoneTest.php
• tests/Browser/ConnectChannelDialogTest.php
• tests/Browser/ConnectConfirmationTest.php
• tests/Browser/ConnectSwitchAccountTest.php
• tests/Browser/CreateFeedsTest.php
• tests/Browser/CreateIdeaEditorTest.php
• tests/Browser/CreateIdeasBoardTest.php
• tests/Browser/CreateShellTest.php
• tests/Browser/CreateTemplatesTest.php
• tests/Browser/DarkModeSurfacesTest.php
• tests/Browser/DialogFooterTest.php
• tests/Browser/DialogFullScreenMobileTest.php
• tests/Browser/ImageCropperTest.php
• tests/Browser/ImportedPostCardTest.php
• tests/Browser/InsightsChannelFilterTest.php
• tests/Browser/InsightsParityTest.php
• tests/Browser/LabelFilterPopoverTest.php
• tests/Browser/LabelRowMenuTest.php
• tests/Browser/LinkCardPreviewTest.php
• tests/Browser/McpSettingsTest.php
• tests/Browser/MediaEditorTest.php
• tests/Browser/MediaLightboxTest.php
• tests/Browser/MemberAccessDialogTest.php
• tests/Browser/NotificationPreferencesTest.php
• tests/Browser/PostApprovalsTest.php
• tests/Browser/PostCardFooterTest.php
• tests/Browser/PostCardLabelsTest.php
• tests/Browser/PostComposerDialogTest.php
• tests/Browser/PostDetailsDialogTest.php
• tests/Browser/PostDetailsGroupTest.php
• tests/Browser/PostNotesTest.php
• tests/Browser/PostRecurrenceTest.php
• tests/Browser/PreferencesPageTest.php
• tests/Browser/ProfilePasswordRequirementsTest.php
• tests/Browser/ProfileTabsTest.php
• tests/Browser/PublishCardActionsTest.php
• tests/Browser/PublishListSkeletonTest.php
• tests/Browser/PublishPageTest.php
• tests/Browser/PublishQueueTest.php
• tests/Browser/ReferralSourceSurveyTest.php
• tests/Browser/RepurposeAccountHealthTest.php
• tests/Browser/RepurposeTest.php
• tests/Browser/SettingsListRowTest.php
• tests/Browser/SettingsSidebarTest.php
• tests/Browser/SidebarChannelReorderTest.php
• tests/Browser/SidebarChannelsTest.php
• tests/Browser/SidebarLanguageSwitchTest.php
• tests/Browser/SidebarMenuTest.php
• tests/Browser/SignaturesPageTest.php
• tests/Browser/SignupPreferencesTest.php
• tests/Browser/WebhookCreateDialogTest.php
• tests/Browser/WebhookDeleteTest.php
• tests/Browser/WebhookShowTest.php
• tests/Browser/WelcomeHeaderTest.php
• tests/Browser/WelcomeMcpTest.php
• tests/Browser/WelcomeMobileTest.php
• tests/Browser/WelcomePlanTest.php
• tests/Browser/WorkspaceCreateTest.php
• tests/Browser/WorkspaceInsightsTest.php
• tests/Browser/WritingAssistantTest.php
• tests/Browser/XLinkDefusingTest.php
• tests/Browser/XLongPostComposerTest.php
• tests/Browser/YouTubeDescriptionTest.php