fix(tasks): expand latest plan after cloud resume

[puemos]

Problem

When a cloud task reconnects with a plan as its latest useful output, history replay marks the plan as historical and the UI folds it. This makes a resumed plan-mode task look like it lost its final state.

Why: Resuming an interrupted task should preserve the visibility of the result the user was last working from.

Changes

• Mark a historical plan for initial expansion only when it is the final replayed item.
• Initialize that plan open while keeping older historical plans folded.

How did you test this?

• pnpm exec vitest run src/adapters/codex-app-server/codex-app-server-agent.test.ts
• pnpm exec vitest run src/features/sessions/components/session-update/PlanApprovalView.test.tsx
• pnpm --filter @posthog/agent typecheck
• pnpm --filter @posthog/ui typecheck
• node scripts/check-host-boundaries.mjs

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

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Created with PostHog Code

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit d8f3ee7.}