bug: error behavior in TUI is inconsistent

### Problem
error behavior is inconsistent. when clicking dev with no agents it exits the tui, when entering logs with no agent, it displays an error in the tui. likely want to converge on the second one.

### Definition of Done
- Converge TUI behavior to consistent error handling behavior.
- Regression test for ensuring this is consistent.

Locate the TUI handlers for clicking dev with no agents and entering logs with no agent, then compare their error paths. Run the existing TUI test suite or relevant tests and add a regression test showing both cases use the same in-TUI error behavior; done means the TUI no longer exits for the dev case.

Written by the indexing model from the issue text.