fix(command-center): guard ActionSelector Enter against empty/stale options

[posthog]

Problem

Users in command center hit a full-screen crash when pressing Enter to approve an agent permission or switch mode (accept edits / plan / default), forcing an app restart or navigating away and back.

The root cause: selectCurrent() in useActionSelectorState.ts read allOptions[selectedIndex] and dereferenced selected.id with no bounds check — unlike its siblings selectByIndex and handleClick, which already guard. When the options change mid-render (a permission gets resolved or superseded, a step/mode transition fires, or the clamping effect hasn't run before the keydown), selected is undefined and selected.id throws a TypeError.

This took down the entire screen, not just the one prompt: command center mounts one ActionSelector per grid cell, and there was no error boundary around individual cells — the only boundary was the app-root one, so a single throw unmounted the whole router tree and showed "Something went wrong."

Why: approving agent permissions / switching mode is a core, high-frequency interaction, so a full-screen crash there is disruptive enough that recovery required restarting the app or navigating away.

Changes

• Add the missing if (!selected) return; guard to selectCurrent, matching the guards selectByIndex and handleClick already have.
• As defense in depth, wrap each command-center grid cell in its own ErrorBoundary so one cell's failure can no longer take down the whole screen (resets when the cell's task/terminal changes).
• Add regression tests covering the empty-options and stale-index cases, plus a happy-path assertion.

How did you test this?

• Added useActionSelectorState.test.ts (3 cases) — all pass via vitest run.
• pnpm --filter @posthog/ui typecheck — clean.
• biome check on the changed files — clean.

Automatic notifications

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

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Created with PostHog Code from an inbox report.

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[github-actions]

React Doctor found no issues in the changed files. 🎉

_{Reviewed by React Doctor for commit ec46443.}