probe: name the MathNode fields; the build baseline is now one warning

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

docs/claude/verification.md

@@ -15,23 +15,21 @@ xvfb-run -a env UDPSCOPE_EXIT_AFTER_MS=8000 UDPSCOPE_ENABLE_ALL_MS=1000 \
 
 Two baselines every run is read against. The UDPS runs must be **unchanged by the source-plugin work**:
 a UDPS self-check, number-normalised (`sed 's/[0-9.]\+/N/g'`), diffs empty against one taken before it.
-A clean build emits **three** warnings and no more: two
-`-Wmissing-field-initializers` on `MathNode::source` and one `-Woverlength-strings` on the icons'
+A clean build emits **one** warning and no more: a `-Woverlength-strings` on the icons'
 generated GResource `.c`, whose blob is **9248** against C99's 4095-byte string-literal limit with
 the five action icons and the two app icons that remain (a note about a generated file, which GCC
-itself supports). The *fourth* was the help pages' generated `.c` (**516044** bytes); the manual is
-now a Mallard set installed for Yelp rather than a GResource compiled into the binary, so that
-bundle — and its warning — is gone, and the baseline moved from four to **three**. Re-measure by
-touching each `*.gresource.xml` under `src/` and rebuilding; a third `-Wmissing-field-initializers`
-or any other warning is a finding. (The fifth warning that used to appear here was an unused
-`output_built` in `math_probe()`; it was **deleted** as dead code — redundant with the
-`output_after_add` already printed on the same line — which dropped the baseline from five to
-four.) And an exit-dump run emits **no** `Gtk-CRITICAL` at all, nor any `Gtk-WARNING`: the dump's
+itself supports). History: the help pages' generated `.c` (**516044** bytes) went when the manual
+became a Mallard set installed for Yelp; an unused `output_built` in `math_probe()` was deleted as
+dead code; and the last two, `-Wmissing-field-initializers` on `MathNode::source` in `math_probe()`,
+went when the probe's `MathNode{MathOp::Gain, {}}` / `MathNode{MathOp::LowPass, {}}` named the
+field (a partial brace-initialiser on `MathNode` re-adds one: `source` has no default member
+initialiser). Re-measure by touching `src/icons/udpscope.gresource.xml` and rebuilding; any
+second warning is a finding. And an exit-dump run emits **no** `Gtk-CRITICAL` at all, nor any `Gtk-WARNING`: the dump's
 `gtk warnings:` line counts GTK's own log (through a writer function — GTK is built with structured
 logging, so the handler API never sees its messages) and must read `0`; see
 [probe-readings.md](probe-readings.md).
 
-An *incremental* build reads **one** of those three: the generated GResource `.c` is not recompiled
+An *incremental* build reads **zero**: the generated GResource `.c` is not recompiled
 when only `src/` changed, so its `-Woverlength-strings` does not reappear.
 
 A third reading every run offers for free: **how many `[udpscope] buffer allocated:` lines it