working on todo.md features

docs/claude/build-and-run.md

@@ -36,14 +36,24 @@ file's basename is that same string, which is what associates a running window w
 
 Options: `--server`, `--port`, `--multicast`, `--interface`, `--buffer-mb` (per
 buffer, default 200), `--max-window`, `--holdoff`, `--recv-buffer`, `--plots` (the row
-count to *start* with, 1..`RowSet::kMaxRows`; the layout editor owns it afterwards).
+count to *start* with, 1..`RowSet::kMaxRows`; the layout editor owns it afterwards),
+`--capture-packets N` (the raw-datagram ring of README's "Packet capture"; 1..100000,
+the value is required, and the popover button uses 1000 when the flag was absent).
+The flag is **not** persisted in the session file: persistence of the enable state
+belongs with `todo.md` item 3, alongside the relative-time toggle.
 
 Run with no `--server` and udpscope asks which source to open: the sessions it has stored, plus a
 form for a new host. Every probe below passes `--server`, so none of them sees it.
 
 `deps/plotter` is built from source with only the GTK4 adapter enabled
 (`PLOT_BUILD_GTK4`); its tests and examples are forced off. `deps/udpsclient` is a
-vendored C99 source pair compiled into a static lib.
+vendored C99 source pair compiled into a static lib. `deps/udpsclient` gained one
+additive entry point for the packet capture — `udps_client_set_datagram_cb()`, firing
+inside `udps_client_poll()` immediately after the UDP `recv()` returns, before the
+magic check or reassembly — plus the public `UDPS_MAX_DATAGRAM_BYTES` the capture
+sizes its slots from. A separate setter, not a fourth parameter on
+`udps_client_set_callbacks()`: that signature has call sites, and a capture hook is no
+reason to change them.
 
 **libadwaita ≥ 1.8 is a system dependency** (`pkg_check_modules(ADWAITA ... libadwaita-1>=1.8)`),
 for two widgets: the shortcut overview (`AdwShortcutsDialog`) and the About dialog