fix(test): stabilize OutroScreen preserveFiles K-test process.exit spy

[kelsonpw]

Summary

The K-keystroke tests in OutroScreen.preserveFiles.test.tsx were
using a per-test vi.spyOn(process, 'exit').mockImplementation(...)
pattern paired with exitSpy.mockRestore() in cleanup. The K
keystroke triggers a fire-and-forget wizardSuccessExit(10) chain
which is fully asynchronous — under CI load the chain landed AFTER
the spy was restored, hit the real process.exit, and vitest's
interceptor surfaced it as an unhandled rejection 24s+ after the
file's tests reported green.

This same flake recurred across six salvage PRs (#765–771).

Fix

Move the vi.spyOn(process, 'exit') to a file-level
beforeAll / afterAll, so there is no window between test
completion and spy restore where the real process.exit is
reachable.

Test plan

• OutroScreen.preserveFiles.test.tsx — all 6 tests pass locally
• No behavior change — pure test-harness fix

🤖 Generated with Claude Code

---

Note

Low Risk
Low risk: test-harness-only change that adjusts process.exit stubbing scope to eliminate CI flakiness, with no production behavior impact.

Overview
Prevents CI flakes in OutroScreen.preserveFiles.test.tsx by moving the process.exit spy from per-test setup/teardown to a file-level beforeAll/afterAll, avoiding a race where an async wizardSuccessExit call could hit the real exit after mockRestore().

Removes redundant per-test process.exit spies/restore calls and updates the Vitest imports accordingly.

^{Reviewed by Cursor Bugbot for commit b25f7a6. Bugbot is set up for automated code reviews on this repo. Configure here.}