Show an Envelope node as a device with its ADSR curve (#388)

The Compressor, the Gain and the Chip are devices in the graph. The
Envelope was still a list of rows, and its shape was left to the
imagination of whoever read the numbers.

- The node is a plate of 520x280 in pale sea green. Its inputs are
  on the left, out and value on the right.
- A dark screen draws the curve over a note in amber. A letter sits
  above each stage, its time below it, and the sustain in percent
  above its line.
- The time on the screen is squeezed. Each stage is as wide as the
  root of its seconds, at least 3 %, and the hold has a fixed fifth.
  So 5 ms of attack still shows beside a release of 3 s.
- The falls use SETTLE, as the player does. With sustain 0 there is
  no hold and no release, and the screen says NOTE ENDS.
- Attack, Decay, Sustain and Release are chrome knobs. The times use
  taper 4, so 5 ms sits an eighth of the way and 1 s not quite half.
- From and To have no range a knob could turn through. They are
  NumberFields on the plate, typed in or scrubbed.
- The decay at sustain 1 and From/To while nothing takes value are
  faded. While a link takes value, the bezel says what it moves
  between, as VALUE 400 TO 3500. The UI font has no arrow.
- Instrument presets give an Envelope 3 columns of 240.
- Test hook __gm.envelope.panel(nodeId).

Tests:
- Unit envelope-view: 6 new tests for the plate, the knob turn, the
  idle settings and the curve. A linear decay turns two of them red.
- e2e 34 (atx): 1 new check on the Laser preset (device between its
  ports, curve ends with the decay, decay knob and scrubbed To field
  each one undo step).
- Probe pictures on stein2: Synth Brass preset, pad, pluck, organ
  and an Envelope whose value moves a Chip.
- Gate (atx): CHECK EXIT 0, 286 files, 4383 tests. The first run was
  red on the font test (#214) for an arrow in the bezel text.

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

README.md

@@ -47,7 +47,7 @@ npm run build        # writes dist/ and regenerates index.html; the folder is wh
 The browser suite and the three example games need a machine with a GPU:
 
 ```bash
-node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1962 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1963 checks (GM_STEPS=20 for one step)
                                                    #   every tool signs in first – see the Accounts page
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs