[codex] Phase 3I: provider and account updates

[sukar0972]

Summary

• add Claude Sonnet 5 as the default Claude model and built-in Claude provider option
• update Claude model aliases/placeholders to canonical claude-sonnet-5
• add a T3 Connect Mobile clients page inside the existing Cloud account UserButton

Upstream

• adapts web-safe portions of upstream 9d66b104f and the non-duplicative account-controls portion of 8cc9a6fa6
• intentionally defers 6672a1d21 Clerk lockfile churn and a7e43b228 Vite Plus bundled-dev upgrade
• skips moving publish-agent-activity controls into ConnectionsSettings because this fork already has that control in Cloud Settings

Grok Composer 2.5 review

• verdict: approve with suggestions; no blockers
• Grok asked to verify SmartphoneIcon import and Clerk custom profile-page API; both are covered by typecheck

Verification

• vp test packages/shared/src/model.test.ts apps/web/src/components/clerk/MobileClientsUserProfilePage.logic.test.ts
• vp run typecheck
• vp check

Notes

• Existing unrelated warnings remain: ProcessResourceMonitor.ts Effect suggestion during typecheck and pre-existing react(no-unstable-nested-components) warnings during vp check.