cleaned up ui added exporter

CLAUDE.md

@@ -45,6 +45,9 @@ xvfb-run -a env UDPSCOPE_EXIT_AFTER_MS=8000 UDPSCOPE_ENABLE_ALL_MS=1000 \
   `UDPSCOPE_TRIG_TRACE_MS` — schedule individual probes.
 - `UDPSCOPE_PROBE_PAUSE_MS` — pause acquisition mid-run so layout numbers are
   measured on a still picture.
+- `UDPSCOPE_EXPORT_MS` (+ optional `UDPSCOPE_EXPORT_PATH`, default
+  `/tmp/udpscope-export`) — collect the export table and write it both ways, skipping
+  only the file chooser.
 
 **Run one self-check at a time.** Two concurrent `xvfb-run -a` instances end up on the
 same display and the second gets no GL context — it dumps `layout over 0 frames` and
@@ -106,6 +109,17 @@ Two lines of the self-check output are assertions in disguise:
   is the same class of bug, not rounding: `publish_event()` clamps the slice to every
   value ring's `produced()`, so publishing before each channel of the latching sample
   has been pushed silently drops it.
+- `[export-probe] mode=.. axis=[a..b] rows=N cols=M time=[c..d] stream=[..]` (stderr,
+  `UDPSCOPE_EXPORT_MS`) — **`time=` must equal `axis=`** and **`rows=` must be the
+  span times the stream's real rate, plus one** (2 s at 10 kS/s is 20001). The export
+  is the *visible* range at the *stored* rate, so a count far short of that is a table
+  cut from the LOD pyramid, and a `time=` narrower than `axis=` is a window searched on
+  the wrong clock (the live branch subtracts `display_epoch()` before searching the
+  ring). In `mode=event`, `stream=` must be the edge ± the window; in `mode=live` it
+  equals `time=`. The two `bytes=` lines are the writers: the `.npy` is
+  `64·⌈(10+len(header)+1)/64⌉ + rows·(16 + 4·cols)`, so a size that is not that is a
+  mispacked record. Read it back with `pd.DataFrame(np.load(path))` after changing
+  either writer.
 
 The probes are the regression net — when changing UI or plot-host behaviour, extend
 the probe/dump in `src/ui.cpp` rather than adding a separate harness.
@@ -154,6 +168,10 @@ Layers to keep straight:
   the live follow (the *group's* — a member's own axis must be `XFollow::Off`, since
   `Figure::link_x()` refuses a `Live` member), the left gutter and the crosshair.
 
+- `ExportTable` (`src/export.hpp`) — the visible window as columns, collected from the
+  snapshot or the live rings and handed to the `.npy`/`.csv` writers. Always the stored
+  samples, never the LOD pyramid's buckets.
+
 `src/ui.cpp` is the GTK4 window (toolbar, trigger panel, signal panel, plot box) plus
 the `tick()` frame function that binds, updates the trigger state and rewrites the
 status line. One `plot::gtk4::PlotArea` in figure mode draws the whole figure. It is by
@@ -239,6 +257,20 @@ far the largest file.
   every value ring.** That is what makes `stamps` and each `values[c]` equal-length
   and index-aligned by construction instead of by two truncations that can disagree —
   `EventSeries::gather()` indexes both at the same `i`.
+- **`live_window_locked()` is the one live cut, shared by `publish_event()` and the
+  export.** Both need the same absolute index range over the time ring and every value
+  ring, or an export and a capture of the same window would hold different samples. Call
+  it under `mutex()`.
+- **A trace's colour is indexed by *signal*, not by trace slot.** `Row::color_index`
+  stores it and `signal_color_index()` (ui.cpp) computes it from the signal list, so a
+  signal dropped on two rows is one colour and the signal panel's chip names a trace
+  unambiguously. `plot::Plot` fixes a colour at `add_trace()`, so changing one needs a
+  figure rebuild — which `assign()` already forces. A signal on no plot gets
+  `RowSet::unplotted_color()` (grey) rather than no chip, so the panel's rows stay the
+  same height.
+- **The export is collected at click time, not in the file-dialog callback.** The live
+  view keeps scrolling while the chooser is up, so a late collection would write a
+  window the user never saw. The writer is picked by the chosen path's extension.
 - **The header bar's buttons are icon-only**, so headless probes must reach them
   through the `App` pointers (`trigger_toggle`, `pause_button`, …), not via
   `find_labelled_button()`. The Arm/Disarm button in the trigger panel still has text.