fix: widen undo dialog and polish its summary line

The undo/redo confirmation dialog capped at 60 columns and wrapped
even a short insert on wide terminals, showed a lowercase "snapshot
taken", a raw ISO-8601 timestamp, and lowercase yes/no labels.

Grow the dialog to fit its longest line (bounded 34–100), capitalise
Snapshot/Yes/No, and render the snapshot timestamp in local time,
human-formatted (24 May 2026, 11:00) via a new chrono dependency
(clock feature only; English month names). Yes/No capitalisation also
applies to the rebuild-confirm dialog.

src/friendly/strings/en-US.yaml

@@ -763,7 +763,7 @@ modal:
   redo_confirm_title: "Redo last undone change"
   undo_confirm_command: "This will undo:"
   redo_confirm_command: "This will re-apply:"
-  undo_confirm_when: "snapshot taken {timestamp}"
+  undo_confirm_when: "Snapshot taken {timestamp}"
   undo_confirm_prompt: "Restore that earlier state?"
   undo_cancelled: "undo cancelled"
   redo_cancelled: "redo cancelled"
@@ -807,8 +807,8 @@ shortcut:
   submit: "submit"
   confirm: "confirm"
   cancel: "cancel"
-  yes: "yes"
-  no: "no"
+  yes: "Yes"
+  no: "No"
   load: "load"
   select: "select"
   browse_path: "browse path"