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

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

docs/claude/build-and-run.md

@@ -13,8 +13,11 @@ cmake --build build
 
 ./build/udpscope --server 127.0.0.1 --port 8000
 ./build/udpscope --server 10.0.0.5 --port 8000 --multicast 239.1.2.3 --interface 10.0.0.9
+./build/udpscope --source udps --source-opt server=127.0.0.1 --source-opt port=8000   # same as --server/--port
 ```
 
+`--help` lists the registered source kinds.
+
 The app can be launched from the shell rather than only from a terminal, but only on request:
 
 ```sh
@@ -96,7 +99,9 @@ prefix-wide target *is* that rule, reached through the `Help` component
 (`cmake --install --component Help`) — and the ordinary `cmake --install` still installs every
 component, so its behaviour is unchanged.
 
-Options: `--server`, `--port`, `--multicast`, `--interface`, `--buffer-mb` (per
+Options: `--source NAME` and the repeatable `--source-opt k=v` (the source kind and its settings;
+`--server`, `--port`, `--multicast` and `--interface` populate the UDPS entries of the same 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),
 `--capture-packets N` (the raw-datagram ring of README's "Packet capture"; 1..100000,