docs: the sample budget in samples per signal, the memory limit and the planner probe lines

Converts every --buffer-mb / buffer_mb mention to --buffer-samples / buffer_samples,
records the unit change as a deviation (README, SPECS, CLAUDE.md), documents the
buffer: and planner: dump lines and the new Preferences row, and updates the help
pages and the help-shot script.

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

docs/claude/build-and-run.md

@@ -101,8 +101,10 @@ component, so its behaviour is unchanged.
 
 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
+`--server`, `--port`, `--multicast`, `--interface`, `--buffer-samples` (samples
+per acquired signal, default 10M, k/M/G suffixes, rounded down to a power of two),
+`--memory-limit-mb` (hard ceiling on the ring bytes, default 8192; also a Preferences row),
+`--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,
 the value is required, and the popover button uses 1000 when the flag was absent).