refactor: Unify substream actions into substream_{on,off} (#2497)

## Summary

- Collapse `live_substream_{on,off,select}` into a unified
`substream_{on,off}` pair, symmetric with `call_{start,end}`.
- Rename the `camera` field on the former `live_substream_select` to
`stream` (it always was a stream ID).
- Add optional `camera` field to both new actions for targeting a
non-selected base camera.
- YAML configs are migrated automatically; URL bookmarks must be updated
by hand.

## Migration

### Cycling between camera and substream (toggle button)

Before:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: live_substream_on
```

After:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: substream_on
```

### Selecting a specific substream

Before:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: live_substream_select
  camera: camera.front_door_hd
```

After:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: substream_on
  stream: camera.front_door_hd
```

### Turning the substream off

Before:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: live_substream_off
```

After:
```yaml
tap_action:
  action: custom:advanced-camera-card-action
  advanced_camera_card_action: substream_off
```

### URL querystrings (manual update required)

| Before | After |
| --- | --- |
|
`?advanced-camera-card-action.live_substream_select=camera.front_door_hd`
| `?advanced-camera-card-action.substream_on=camera.front_door_hd` |

tests/card-controller/actions/factory.test.ts

@@ -40,7 +40,6 @@ import { SleepAction } from '../../../src/card-controller/actions/actions/sleep'
 import { StatusBarAction } from '../../../src/card-controller/actions/actions/status-bar';
 import { SubstreamOffAction } from '../../../src/card-controller/actions/actions/substream-off';
 import { SubstreamOnAction } from '../../../src/card-controller/actions/actions/substream-on';
-import { SubstreamSelectAction } from '../../../src/card-controller/actions/actions/substream-select';
 import { ToggleAction } from '../../../src/card-controller/actions/actions/toggle';
 import { UnmuteAction } from '../../../src/card-controller/actions/actions/unmute';
 import { URLAction } from '../../../src/card-controller/actions/actions/url';
@@ -111,18 +110,8 @@ describe('ActionFactory', () => {
       [{ advanced_camera_card_action: 'fullscreen' as const }, FullscreenAction],
       [{ advanced_camera_card_action: 'info' as const }, InfoAction],
       [{ advanced_camera_card_action: 'image' as const }, ViewAction],
-      [
-        { advanced_camera_card_action: 'live_substream_off' as const },
-        SubstreamOffAction,
-      ],
-      [{ advanced_camera_card_action: 'live_substream_on' as const }, SubstreamOnAction],
-      [
-        {
-          advanced_camera_card_action: 'live_substream_select' as const,
-          camera: 'camera.office',
-        },
-        SubstreamSelectAction,
-      ],
+      [{ advanced_camera_card_action: 'substream_off' as const }, SubstreamOffAction],
+      [{ advanced_camera_card_action: 'substream_on' as const }, SubstreamOnAction],
       [{ advanced_camera_card_action: 'live' as const }, ViewAction],
       [
         {