Agents: `Esc` sometimes doesn't work for changes modal

[bamurtaugh]

Reported by @TylerLeonhardt and I can repro:

• click on a file in changes -> opens in overlay editor
• hit ESC -> the view hides 🆗
• click on a file in changes -> opens in overlay editor
• click on a different file in that overlay editor
• 🐛 ESC does nothing

[lostintangent]

Yeah it seems like ESC cancels a tree focus when you explicitly select an item. And then after hitting ESC in that state, the focus doesn't seem to be clear 🤔 If you click in a file/diff, then ESC works as expected, so it seems to be specific to the interactions with the file tree.