feat(tui): bare /details opens a keyboard selector

DetailsDialog is a centered SelectList over the five transcript-detail
states (three tool-card phases, reasoning shown/hidden); it preselects
the current phase, marks both current values, applies on Enter, and
cancels on Esc/Ctrl+C. Width is the new detailsDialogWidth config key.
The argument grammar is unchanged and shares the same setters.

packages/ui/tui/tests/snapshots/details-command.expected.txt

@@ -1,7 +1,7 @@
 terminal 100x40 buffer=normal length=40 base=0 viewport=0
 lifecycle started=1 stopped=0 progress=inactive
 title "DSH snapshot"
-cursor hidden column=7 viewportRow=19 bufferRow=19
+cursor hidden column=7 viewportRow=17 bufferRow=17
 buffer
 0| " DEEPSEEK HARNESS"
   style 1-8 fg=bright-magenta bold
@@ -29,17 +29,14 @@ buffer
 14| "Tool cards hidden.                                                                                  "
   style 0-17 dim
 15| <blank>
-16| "Tool and context cards hidden; reasoning blocks hidden.                                             "
-  style 0-54 dim
-17| <blank>
-18| "/workspace/project (tui-staging)  deepseek-v4-flash  ↑0 ↓0  0% context"
+16| "/workspace/project (tui-staging)  deepseek-v4-flash  ↑0 ↓0  0% context"
   style 0-17 fg=bright-magenta bold
   style 18-31 dim
   style 34-50 dim
   style 53-57 dim
   style 60-69 dim
-19| " dsh >                                                                                              "
+17| " dsh >                                                                                              "
   style 1-3 fg=bright-magenta bold
   style 5-6 dim
   style 7-7 inverse
-20-39| <blank>
+18-39| <blank>