docs: the source-plugin framework, the --source options and the source-kinds probe

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

CLAUDE.md

@@ -5,7 +5,8 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 ## What this project is
 
 udpscope is a **GTK4 oscilloscope-style viewer for a UDPStreamer source**. It receives one
-UDP stream with `deps/udpsclient`, buffers it in a large ring (default 200 MB), and draws it
+data source -- a UDPStreamer stream through `deps/udpsclient` by default, or another registered
+source kind (see `docs/claude/architecture.md`) -- buffers it in a large ring (default 200 MB), and draws it
 with `deps/plotter` — a figure of up to eight stacked rows sharing one x window. On top of
 the live view it provides the things a bench scope provides: a trigger with a pre/post event
 window, a pause that freezes the visible window, cursors, statistical measurements,
@@ -20,7 +21,7 @@ Two documents bound the work and are **not** interchangeable with this one:
 
 Three things shape almost every change here, and the linked files expand on each:
 
-- **There are exactly two threads** — a producer that owns the UDP client and the GTK main
+- **There are exactly two threads** — a producer that owns the data source and the GTK main
   thread that owns every widget and the GL context — and they share `ScopeModel` under one
   mutex. Samples cross through lock-free rings, never through the lock.
 - **There is no unit test suite.** The only automated check is the application's own headless
@@ -45,7 +46,7 @@ The detail lives in `docs/claude/`. Read the files that touch the area you are e
 
 | File | What it covers |
 | --- | --- |
-| [architecture.md](docs/claude/architecture.md) | The two threads and what they share; the one `BufferStore` and the four display modes (`Live`, `Capturing`, `Held`, `Waiting`); the display clock and `stream_at_x0()`; the layers to keep straight (`SignalInfo` → `ChannelBuffer` → `SlotSeries` → `RowSet`). |
+| [architecture.md](docs/claude/architecture.md) | The two threads and what they share; the one `BufferStore` and the four display modes (`Live`, `Capturing`, `Held`, `Waiting`); the display clock and `stream_at_x0()`; the layers to keep straight (`SignalInfo` → `ChannelBuffer` → `SlotSeries` → `RowSet`); the source plugins. |
 
 ### Invariants worth knowing before editing