refactor(decnet_web/DeckyFleet): move IntervalEditor out

Verbatim move of the per-decky mutation-interval modal (~60 LOC)
into its own file. Saves null when the toggle is off, minutes
otherwise.

- New DeckyFleet/IntervalEditor.tsx
- IntervalEditor.test.tsx covers null-current disabled path,
  numeric-current enabled path, and CANCEL not firing onSave.
- src/test/fixtures/decky.ts now derives DeckyFixture from the
  canonical Decky type (the fixture's loose swarm shape was
  missing host_address/host_status; aligning to Decky catches
  that statically).

decnet_web/src/components/DeckyFleet.tsx

@@ -1004,67 +1004,7 @@ const DeployWizard: React.FC<DeployWizardProps> = ({
   );
 };
 
-// ─── Interval editor modal ───────────────────────────────────────────────
-
-interface IntervalEditorProps {
-  open: boolean;
-  deckyName: string;
-  current: number | null;
-  onClose: () => void;
-  onSave: (minutes: number | null) => void;
-}
-
-const IntervalEditor: React.FC<IntervalEditorProps> = ({ open, deckyName, current, onClose, onSave }) => {
-  const [enabled, setEnabled] = useState<boolean>(current !== null);
-  const [minutes, setMinutes] = useState<number>(current ?? 30);
-
-  return (
-    <Modal
-      open={open}
-      onClose={onClose}
-      title={`MUTATION INTERVAL · ${deckyName}`}
-      icon={RefreshCw}
-      accent="violet"
-      footer={
-        <>
-          <button className="btn ghost" onClick={onClose}>CANCEL</button>
-          <button className="btn violet" onClick={() => onSave(enabled ? minutes : null)}>SAVE</button>
-        </>
-      }
-    >
-      <div className="modal-body">
-        <div style={{ display: 'flex', gap: 10, alignItems: 'center', padding: 14, border: '1px solid var(--border)' }}>
-          <input
-            id="interval-enable"
-            type="checkbox"
-            checked={enabled}
-            onChange={(e) => setEnabled(e.target.checked)}
-            style={{ accentColor: 'var(--matrix)' }}
-          />
-          <label htmlFor="interval-enable" style={{ fontSize: '0.8rem', letterSpacing: 1 }}>
-            ENABLE PERIODIC MUTATION
-          </label>
-        </div>
-        {enabled && (
-          <div className="tweak-group">
-            <label>INTERVAL ({minutes} minutes)</label>
-            <input
-              type="range"
-              min={5}
-              max={240}
-              step={5}
-              value={minutes}
-              onChange={(e) => setMinutes(parseInt(e.target.value, 10))}
-            />
-            <div className="dim" style={{ fontSize: '0.65rem', letterSpacing: 1 }}>
-              Applied on the next mutation cycle.
-            </div>
-          </div>
-        )}
-      </div>
-    </Modal>
-  );
-};
+import { IntervalEditor } from './DeckyFleet/IntervalEditor';
 
 // ─── Fleet page ──────────────────────────────────────────────────────────
 

decnet_web/src/components/DeckyFleet/IntervalEditor.test.tsx

@@ -0,0 +1,62 @@
+import { describe, it, expect, vi } from 'vitest';
+import { render, screen } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { IntervalEditor } from './IntervalEditor';
+
+describe('IntervalEditor', () => {
+  it('starts disabled when current is null and saves null', async () => {
+    const onSave = vi.fn();
+    const user = userEvent.setup();
+    render(
+      <IntervalEditor
+        open
+        deckyName="decoy-01"
+        current={null}
+        onClose={() => {}}
+        onSave={onSave}
+      />,
+    );
+    const checkbox = screen.getByLabelText('ENABLE PERIODIC MUTATION') as HTMLInputElement;
+    expect(checkbox.checked).toBe(false);
+    expect(screen.queryByText(/INTERVAL \(/)).not.toBeInTheDocument();
+
+    await user.click(screen.getByText('SAVE'));
+    expect(onSave).toHaveBeenCalledWith(null);
+  });
+
+  it('starts enabled when current is a number and saves the slider value', async () => {
+    const onSave = vi.fn();
+    const user = userEvent.setup();
+    render(
+      <IntervalEditor
+        open
+        deckyName="decoy-02"
+        current={45}
+        onClose={() => {}}
+        onSave={onSave}
+      />,
+    );
+    expect(screen.getByText(/INTERVAL \(45 minutes\)/)).toBeInTheDocument();
+
+    await user.click(screen.getByText('SAVE'));
+    expect(onSave).toHaveBeenCalledWith(45);
+  });
+
+  it('CANCEL invokes onClose without onSave', async () => {
+    const onClose = vi.fn();
+    const onSave = vi.fn();
+    const user = userEvent.setup();
+    render(
+      <IntervalEditor
+        open
+        deckyName="decoy-03"
+        current={30}
+        onClose={onClose}
+        onSave={onSave}
+      />,
+    );
+    await user.click(screen.getByText('CANCEL'));
+    expect(onClose).toHaveBeenCalledTimes(1);
+    expect(onSave).not.toHaveBeenCalled();
+  });
+});

decnet_web/src/components/DeckyFleet/IntervalEditor.tsx

@@ -0,0 +1,71 @@
+import React, { useState } from 'react';
+import { RefreshCw } from '../../icons';
+import Modal from '../Modal/Modal';
+
+interface Props {
+  open: boolean;
+  deckyName: string;
+  current: number | null;
+  onClose: () => void;
+  onSave: (minutes: number | null) => void;
+}
+
+/** Modal that toggles + slider-edits per-decky mutation intervals.
+ *  Saves null when disabled, minutes otherwise. */
+export const IntervalEditor: React.FC<Props> = ({
+  open,
+  deckyName,
+  current,
+  onClose,
+  onSave,
+}) => {
+  const [enabled, setEnabled] = useState<boolean>(current !== null);
+  const [minutes, setMinutes] = useState<number>(current ?? 30);
+
+  return (
+    <Modal
+      open={open}
+      onClose={onClose}
+      title={`MUTATION INTERVAL · ${deckyName}`}
+      icon={RefreshCw}
+      accent="violet"
+      footer={
+        <>
+          <button className="btn ghost" onClick={onClose}>CANCEL</button>
+          <button className="btn violet" onClick={() => onSave(enabled ? minutes : null)}>SAVE</button>
+        </>
+      }
+    >
+      <div className="modal-body">
+        <div style={{ display: 'flex', gap: 10, alignItems: 'center', padding: 14, border: '1px solid var(--border)' }}>
+          <input
+            id="interval-enable"
+            type="checkbox"
+            checked={enabled}
+            onChange={(e) => setEnabled(e.target.checked)}
+            style={{ accentColor: 'var(--matrix)' }}
+          />
+          <label htmlFor="interval-enable" style={{ fontSize: '0.8rem', letterSpacing: 1 }}>
+            ENABLE PERIODIC MUTATION
+          </label>
+        </div>
+        {enabled && (
+          <div className="tweak-group">
+            <label>INTERVAL ({minutes} minutes)</label>
+            <input
+              type="range"
+              min={5}
+              max={240}
+              step={5}
+              value={minutes}
+              onChange={(e) => setMinutes(parseInt(e.target.value, 10))}
+            />
+            <div className="dim" style={{ fontSize: '0.65rem', letterSpacing: 1 }}>
+              Applied on the next mutation cycle.
+            </div>
+          </div>
+        )}
+      </div>
+    </Modal>
+  );
+};

decnet_web/src/test/fixtures/decky.ts

@@ -1,21 +1,6 @@
-export interface DeckyFixture {
-  name: string;
-  ip: string;
-  services: string[];
-  distro: string;
-  hostname: string;
-  archetype: string | null;
-  service_config: Record<string, Record<string, unknown>>;
-  mutate_interval: number | null;
-  last_mutated: number;
-  swarm?: {
-    host_uuid: string;
-    host_name: string;
-    state: string;
-    last_error: string | null;
-    last_seen: string | null;
-  };
-}
+import type { Decky } from '../../components/DeckyFleet/types';
+
+export type DeckyFixture = Decky;
 
 export const makeDecky = (overrides: Partial<DeckyFixture> = {}): DeckyFixture => ({
   name: 'decoy-01',