ui: park the slide-over stack only when the dying signal page is the visible one

docs/claude/probe-readings.md

@@ -2637,7 +2637,7 @@ left the caller's `false` alone would read `dock_shown=0 default=1 ok=0`. The pr
 ## `[signalpage]`
 
 ```
-[signalpage] name=sine open=1 pages=1 enable_visible=1 plot_buttons=1 plot_on_row0=1 plot_on_row0_disabled=1 locked_enable_sensitive=0 removed=1 btn_row0=1 back_to_list=1 row_opens=1 pruned=1 rows=1
+[signalpage] name=sine open=1 pages=1 enable_visible=1 plot_buttons=1 plot_on_row0=1 plot_on_row0_disabled=1 locked_enable_sensitive=0 removed=1 btn_row0=1 back_to_list=1 row_opens=1 pruned=1 other_page_kept=1 rows=1
 ```
 
 `UDPSCOPE_PROBE_SIGNAL_PAGES_MS` builds and drives the page of the first streamed signal. `open=1` (the slide-over shows `signal:<name>`), `pages=1`
@@ -2648,7 +2648,9 @@ the same plot), `locked_enable_sensitive=0` (with `signals_locked` set and `sign
 the signal lock -- the same goes for a math channel's Edit graph and Delete, which the probe does not read; the probe restores the lock), `removed=1`
 (the page's "Remove from plots" took it off), `btn_row0=1` (the "Plot on 1" button, the user's path, put it back), `back_to_list=1` ("All signals"
 target), `row_opens=1` (activating the list row opens the page), and `pruned=1`: a math channel's page was opened, its **Delete** button clicked, and
-the slide-over closed and the page was dropped by `signal_pages_sync()`. `pruned=-1` means no math channel could be added; `0` is a stale page.
+the slide-over closed and the page was dropped by `signal_pages_sync()`. `pruned=-1` means no math channel could be added; `0` is a stale page. `other_page_kept=1`: with the `trigger` page open, a signal page that is not on show was pruned (a math channel added, its page built, the
+channel removed) and the slide-over was still on `trigger`, both by `slideover_page()` and by the stack's visible child; `0` is `signal_pages_sync()` parking the stack on the
+signals list while the title and the badge marker still name `trigger`; `-1` when there is no `trigger` page or no math channel could be added.
 
 ## `[badges]`