ui: a slide-over panel over the plot's right edge, with its probe

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/claude/verification.md

@@ -418,6 +418,17 @@ precedent, not an exception.
   defect where the accumulation is gated on the visible tab, which would leave a gap in min/max/avg for
   exactly as long as the trigger was on screen. It enables *and plots* its own signal, so it needs no other
   probe ahead of it. The reading's own entry is in `probe-readings.md`.
+- `UDPSCOPE_PROBE_SLIDEOVER_MS=1500` with `UDPSCOPE_EXIT_AFTER_MS=5000` (and `UDPSCOPE_ENABLE_ALL_MS=500`) -- the
+  slide-over panel over the plot's right edge, opened on a throw-away `probe` page, read 0.5 s later. Two
+  `[slideover]` lines. Line 1 must read `panel=360x<overlay height> ... edge_flush=1 full_height=1
+  outside_hits_plot=1 inside_hits_panel=1 ... plot_unchanged=1`: a 360 px opaque panel flush to the overlay's
+  right edge and as tall as it, a pick outside it landing in the plot and one inside it in the panel, and the
+  plot's width unchanged by the panel being open (`plot_w before=` equal to `open=`).
+  `outside_hits_plot=0` means the panel has an allocation wider than 360 or a transparent parent that
+  swallows the plot's pan, drop and hover; `plot_unchanged=0` means the panel resized the plot. Line 2 must
+  read `click_inside_closes=0 still_open=1 click_outside_closes=1 esc_closes=1 closed=1`. For a screenshot
+  add `UDPSCOPE_PROBE_SLIDEOVER_HOLD=1`, which leaves the page open after line 1 (run with `GSK_RENDERER=cairo`
+  and `import -window root`): the panel must be drawn over the traces, opaque.
 - `UDPSCOPE_PROBE_SOURCE_KINDS=2000` with `UDPSCOPE_EXIT_AFTER_MS=5000`, run as `--source probe --source-opt rate=500`
   -- the source-plugin path end to end. The variable's presence also registers the test-only `probe` kind (a
   synthetic sine with one panel), so it is the only way a run sees that kind; its value is the delay in ms.