feat(billing): notify alpha plan users about june 4 migration

[posthog]

Summary

Updates the Plan and Usage settings so the alpha → free migration on June 4, 2026 is explicit, and stops showing the Pro Upgrade button to alpha users (alpha already grants full Pro access).

Changes

• Alpha plan banner in PlanUsageSettings.tsx now spells out that alpha seats will be moved to the free plan on June 4, 2026 and points users at upgrading to Pro if they want to keep current usage levels.
• Pro plan card action is now hidden when isAlpha is true — no Upgrade button (was shown via the else branch when !(isOrgPro && !isAlpha)), no Cancel/Reactivate (alpha will auto-migrate).

Companion change in posthog dashboard: PostHog/posthog#57629.

Test plan

• pnpm --filter code typecheck (passes)
• pnpm exec biome check apps/code/src/renderer/features/settings/components/sections/PlanUsageSettings.tsx (passes)
• Manual: open Settings → Plan & usage as a user on posthog-code-pro-0-20260422
  • banner copy mentions June 4, 2026 migration to free plan
  • Pro card shows no Upgrade button (and no Cancel button)
• Manual: same screen on a regular Pro user → Cancel/Reactivate still works
• Manual: same screen on a Free user → Upgrade button still works

Agent context

• Tool: PostHog Code (Task 7ad4d917-387c-493f-8dd1-c8b8df698434)
• Prompt: Pawel asked for the alpha → free migration to be explicit in the plan and usage UI and for the Upgrade button to be hidden on alpha. Initially I made the change in the posthog dashboard repo (PR #57629); this PR is the companion in the desktop app.
• Decisions:
  • Reused the existing isAlpha flag at line 79 instead of pushing it into useSeat — only one caller needs it.
  • Hid all Pro-card actions for alpha (not just Upgrade): showing Cancel for an auto-migrating seat would be misleading and isn't in the request.
  • Banner copy is from the spirit of the Slack thread that triggered this; please double-check against the email copy referenced there.

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Created with PostHog Code

[pawel-cebula]

Looks good from my side but didn't test locally (need to set up code for local dev first) so will let you ✅ and merge @k11kirky / @charlesvien

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

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### Issue 1 of 1
apps/code/src/renderer/features/settings/components/sections/PlanUsageSettings.tsx:278-282
**Banner mentions upgrading but provides no path to do so**

The banner tells alpha users they'll "be able to upgrade to the Pro plan" after migration, but the Upgrade button on the Pro card is now hidden for alpha users and there is no link or CTA in the banner itself. A user who reads this and wants to act early has no obvious way to reach the billing or upgrade flow from this screen. Consider adding an `onClick={() => void openBillingPage(billingOrgId)}` link inline in the banner text, or re-showing the Upgrade button (with a tooltip explaining that the upgrade will take effect after June 4) so the copy and the UI are consistent.

_{Reviews (1): Last reviewed commit: "fix(billing): clarify alpha seat expiry ..." | Re-trigger Greptile}