Describe the Gain node as an orange device (#384)

- Sounds: the Gain row says how its node looks and how its knob works.
- Architecture: GainPanel and GainFace, drawPlate shared.
- Development: 1957 editor checks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Architecture.md

@@ -424,7 +424,9 @@ src/editor/soundfx/    SoundFxEditor (#311: the graph, a sound to try it on, Pla
                        ratio to drag, and the levels in and out tinted where it squeezes), CompressorPanel +
                        hardwareView (#379: the Compressor as a device, its meter, LEDs and plate worked
                        out apart from the drawing), CompressorFace + nodeFaces (#380: the panel as what a
-                       Compressor node shows in the graph, #381 the EQ's as well), nodeParamDrag (a knob's drag as one undo
+                       Compressor node shows in the graph, #381 the EQ's as well), GainPanel + GainFace (#384:
+                       the Gain as an orange plate with one knob, `drawPlate` shared with the Compressor),
+                       nodeParamDrag (a knob's drag as one undo
                        step, for the tab and the node), nodeTabs (which nodes open a tab of their own)
 src/editor/instrument/ InstrumentEditor (#331: the graph over the keys, Preset, Randomize, Mutate, Audition),
                        PianoKeyboard + keys (the keys drawn, played by the pointer and the computer keyboard)

Development.md

@@ -19,7 +19,7 @@ php tests/php/accounts.test.php                               # the API's accoun
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
 php tests/php/files.test.php                                  # uploaded files in a folder per account (#344), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1956 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1957 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result

Sounds.md

@@ -424,7 +424,7 @@ response of a Reverb, and as what the Sound FX tab tries out. Its row means noth
 
 | Node | What it does |
 | --- | --- |
-| **Gain** | Louder or quieter, in dB (`Gain (dB)`): 0 leaves it alone, -6 is about half as loud, +6 twice. Above 0 the sound can clip. |
+| **Gain** | Louder or quieter, in dB (`Gain (dB)`): 0 leaves it alone, -6 is about half as loud, +6 twice. Above 0 the sound can clip. In the graph the node is drawn as a small device (#384): the Compressor's brushed plate in orange, 160x220 graph units, with one chrome knob between its inputs and its output. The knob works as the Compressor's do: drag up or down, a double-click resets it to 0 dB, each turn one undo step, the wheel zooms the graph. 0 dB stands straight up, and the quiet end below -24 dB takes only a fifth of the turn. A linked `Gain (dB)` greys the knob. There is no tab and no meter. |
 | **Pitch** | Higher or lower, in semitones (12 is an octave, 0.5 a quarter tone). The sound **keeps its length**, also when the pitch changes while it plays. The pitch is made where the sound is read, so an effect before the Pitch acts as if it came after it. On a [Chip](Instruments#chips) of an instrument it moves the frequency of the Chip itself. Its `wet` takes the semitones from 0 up to all of them, see [below](#bypass-and-wet). |
 | **5-Band-EQ** | Five bands in dB: 80 Hz and 12 kHz as shelves, 250 Hz, 1 kHz and 4 kHz as peaks. A band at 0 does nothing. |
 | **Parametric EQ** | Up to 10 bands, each a filter of its own type, frequency, gain, Q and slope, drawn together as one curve. The node shows its editor right in the graph, and a **double-click on the node's title** opens the same in a tab. Both show the spectrum of what passes the node. A new node has no band and does nothing. See [below](#parametric-eq). |