fix(sandbox): Gracefully handle unavailable sandbox sessions

[sentry]

Previously, when tryRestoreHintedSandbox encountered an unavailable sandbox session (e.g., HTTP 410 Gone from Vercel's Sandbox API), it would re-throw the error. This prevented acquireSandbox from falling back to createFreshSandbox, leading to user-facing errors.

This change modifies tryRestoreHintedSandbox to clear the sandboxRef, invalidate the session, and return null when isSandboxUnavailableError is true. This allows acquireSandbox to correctly proceed with creating a fresh sandbox, improving resilience and user experience.

Additionally, an unrelated oxlint error in packages/junior/tests/component/task-execution/conversation-work.test.ts was fixed by replacing Reflect.get with typed property access to resolve a CI failure.

Fixes JUNIOR-7R

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Project	Deployment	Actions	Updated (UTC)
junior-docs	Ready	Preview	Aug 22, 2026 11:47pm

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

Prepare failure orphans restored sandbox

Medium Severity

After Sandbox.get succeeds, a prepare-time unavailable error now clears sandboxRef and returns null, so acquireSandbox builds a new sandbox. That drops the still-running named VM the old path kept for reconnect, and it never stopSessions the retrieved session, so the prior sandbox can keep burning resources until timeout.

 

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