Edit a Filter in its node and resize EQ and Filter nodes (#385)

A Filter sounds like one band of the Parametric EQ, but it keeps what
the EQ cannot: linked numbers, the all-pass and +-40 dB. So it stays a
node of its own and gets the EQ's editor with itself as the one band.
The editors also stop running out of their room: what does not fit is
left out instead of being cut.

- The curve of the EQ is now BandCurve with a host the EQ and the
  Filter both fill. CurvePanel holds what their panels share.
- FilterPanel shows the Filter as one band. A drag of its handle sets
  frequency and gain as one undo step. A number fed by a link is
  greyed out and the drag leaves it alone.
- A double-click on the Filter's title opens the same in a tab of its
  own. Delete there does nothing, the node stays.
- The Filter is tapped like the EQ, so its node and its tab draw the
  spectrum of what passes it. A tap is two gain nodes per voice, the
  analysers are made only while someone listens.
- EqFace and FilterFace are one CurveFace now, given the panel.
- EQ and Filter nodes have a corner to resize them, drawn like the
  floating window's. The size is saved on the node as `size`, each
  drag is one undo step, the least is 240 x 120.
- In the node the help line is gone. The row of numbers comes in only
  once the curve keeps 120 px of height. A group of the row that does
  not fit is not drawn, the one on the right first.
- A frequency or dB label that would run into the one before it is
  left out.
- The all-pass is drawn flat. The curve's maths takes every shape a
  Filter has.

Found on the way:
- The instrument presets set nodes 240 apart. A Filter with its
  editor is about 700 wide and covered the Bitcrusher, so a Filter
  now takes four columns.

Tests:
- Unit: 8 new (filter band, resize command and save, fitting rules),
  stage lists with a Filter now hold its taps
- e2e 34 (atx): ALL PASSED, 130 checks (4 new)
- Gate (atx): CHECK EXIT 0, 284 files, 4367 tests

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, 1957 checks (GM_STEPS=20 for one step)
+node tools/seed-e2e.mjs && node tools/e2e.mjs      # the editor, 1961 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