Edit a Parametric EQ in a tab of its own (#370)

The EQ's editor floated over the editor as a window since #367. The
user wants it as a tab for now. Whether any tab can float and dock
again is weighed apart from this.

- A double-click on the node asks for the tab through
  `EditorState.openEq`, as `openValues` does for a Variables tab.
- The tab is a document `eq:<asset>:<node>`, one per EQ node. A
  second double-click brings the open one up.
- Its name is the asset's, with `EQ 2`, `EQ 3` when the asset has
  more than one. The icon is the sound FX's.
- The tab closes with its node, its asset, or a new project, through
  the same `syncDocuments` as every document.
- `EqWindow` becomes `EqEditor`, a `VStack` with a `TabHeader`. The
  curve takes the room of the tab, 320 x 160 at least.
- The window's title bar, dragging and Close button are gone.
- Delete in the EQ's tab removes the picked band. It never falls
  through to the selection, which is still the EQ's node.
- The hint below the curve is shorter, it was cut off at 1280 px.

Tests:
- e2e 34 (melektaus-atx): ALL PASSED, 96 checks, 2 rewritten. The
  tab opens on a double-click and goes with its node.
- Gate (melektaus-atx): CHECK EXIT 0, 274 files, 4231 tests.

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

src/editor/debug/graphHooks.ts

@@ -1,6 +1,5 @@
 import { NameTransitionCommand } from '../../core/commands/graphCommands';
 import { currentNodePalette } from '../graph/NodePalette';
-import { currentEqEditor } from '../soundfx/EqEditor';
 import { rectOf } from '../textProbe';
 import { centreOf, snapButton, type HookContext } from './hookHelpers';
 
@@ -117,33 +116,24 @@ export function graphHooks({ state, editor }: HookContext) {
       setParam: (key: string, value: number) => editor.soundFxEditor.setPreviewValue(key, value),
       nodeAt: (nodeId: string) => editor.soundFxEditor.canvas.nodeGlobal(nodeId),
     },
-    /** The Parametric EQ's window (#367): for which node it is open, its bands and where to aim. */
+    /** The Parametric EQ's tab (#367, #370): for which node it is showing, its bands and where to aim. */
     eq: {
-      shown: () => currentEqEditor()?.shownFor ?? null,
-      bands: () => currentEqEditor()?.bands() ?? null,
-      picked: () => currentEqEditor()?.picked ?? null,
-      handleAt: (index: number) => currentEqEditor()?.curve.handleGlobal(index) ?? null,
-      pointAt: (hz: number, db: number) => currentEqEditor()?.curve.pointGlobal(hz, db) ?? null,
+      shown: () => (editor.tab === 'eq' ? editor.eqEditor.shownFor : null),
+      bands: () => editor.eqEditor.bands(),
+      picked: () => editor.eqEditor.picked,
+      handleAt: (index: number) => editor.eqEditor.curve.handleGlobal(index),
+      pointAt: (hz: number, db: number) => editor.eqEditor.curve.pointGlobal(hz, db),
       fields: () => {
-        const eq = currentEqEditor();
-        return (
-          eq && {
-            type: eq.typeButton.text,
-            slope: eq.slopeButton.enabled ? eq.slopeButton.text : null,
-            gain: eq.gainField.enabled ? eq.gainField.value : null,
-            q: eq.qField.enabled ? eq.qField.value : null,
-            frequency: eq.frequencyField.value,
-          }
-        );
-      },
-      typeAt: () => {
-        const eq = currentEqEditor();
-        return eq ? centreOf(eq.typeButton) : null;
-      },
-      closeAt: () => {
-        const eq = currentEqEditor();
-        return eq ? centreOf(eq.closeButton) : null;
+        const eq = editor.eqEditor;
+        return {
+          type: eq.typeButton.text,
+          slope: eq.slopeButton.enabled ? eq.slopeButton.text : null,
+          gain: eq.gainField.enabled ? eq.gainField.value : null,
+          q: eq.qField.enabled ? eq.qField.value : null,
+          frequency: eq.frequencyField.value,
+        };
       },
+      typeAt: () => centreOf(editor.eqEditor.typeButton),
     },
     instrument: {
       current: () => editor.instrumentEditor.currentAssetId,