Add TUI flow tests for execution modes and side effects

[rshelekhov]

Summary

Add automated tests for the most important execution flows, especially around dry-run and parameterized runs.

Why this matters

Execution behavior is now central product logic. It should not rely only on manual testing.

Acceptance Criteria

• Tests cover normal run, dry-run, cancel, and dangerous-target confirmation flows.
• Tests verify side effects are skipped when expected.
• Test structure makes future execution features easier to add safely.

Dependencies

• Dry-run
• Interactive execution parameters