feat(update): add nightly Velopack update channel (#80)

Adds `nightly` as a selectable auto-update channel (Windows + macOS).

Client:
- update-manager.ts: add 'nightly' to UpdateChannel (veloChannel already
  yields win-x64-nightly / osx-arm64-nightly, so no logic change)
- main.ts: allow 'nightly' in the runtime IPC channel guard
- preload.ts: add 'nightly' to the preload-local UpdateChannel union
- screen.js / settings.html: add the Nightly option + helper text

CI (nightly.yml):
- derive <pkg>-nightly.<UTC date> version in the setup job
- setup-dotnet (pinned from .build-config.json) so the vpk CLI has net8,
  matching build.yml
- vpk pack win-x64-nightly / osx-arm64-nightly (mac signed + notarized,
  mirroring build.yml's signed/unsigned fallback)
- publish a rolling `nightly` GitHub Release (prerelease=false, latest=false)
  that the in-app updater reads for the nightly channel
- concurrency guard so an overlapping dispatch can't race the rolling release

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/main/main.ts

@@ -1108,7 +1108,7 @@ async function startup(): Promise<void> {
         // IPC is untyped at runtime — validate the channel string before forwarding
         // so a renderer bug or compromised page can't pass arbitrary values into
         // the Velopack SDK.
-        const VALID_CHANNELS: readonly string[] = ['stable', 'rc', 'beta', 'alpha'];
+        const VALID_CHANNELS: readonly string[] = ['stable', 'rc', 'beta', 'alpha', 'nightly'];
         if (typeof channel !== 'string' || !VALID_CHANNELS.includes(channel)) {
             return updateManager.getStatus();
         }

src/main/preload.ts

@@ -39,7 +39,7 @@ import {
 // from update-manager.ts) so the preload bundle doesn't drag in the Velopack
 // SDK — preload runs in a restricted context and we don't want native
 // require()s evaluated here.
-export type UpdateChannel = 'stable' | 'rc' | 'beta' | 'alpha';
+export type UpdateChannel = 'stable' | 'rc' | 'beta' | 'alpha' | 'nightly';
 export interface UpdateAvailablePayload { version: string; channel: UpdateChannel }
 export interface UpdateDownloadedPayload { version: string; channel: UpdateChannel }
 

src/main/update-manager.ts

@@ -3,7 +3,10 @@
 // Architecture:
 //   - The renderer persists the user's release channel in localStorage and
 //     calls setChannel() on boot so this module's UpdateManager is bound to
-//     the right feed (stable | rc | beta | alpha).
+//     the right feed (stable | rc | beta | alpha | nightly). The nightly feed
+//     is published by .github/workflows/nightly.yml as a rolling `nightly`
+//     GitHub Release (rid channels win-x64-nightly / osx-arm64-nightly),
+//     unlike the tag-driven alpha/beta/rc/stable feeds from build.yml.
 //   - On init() and then every 4 hours we run checkForUpdatesAsync(); when a
 //     hit comes back we download in the background, broadcast
 //     update:available immediately and update:downloaded once the .nupkg is
@@ -41,7 +44,7 @@ import { app, BrowserWindow } from 'electron';
 import type { UpdateInfo } from 'velopack';
 import { IPC_UPDATE_EVENT_AVAILABLE, IPC_UPDATE_EVENT_DOWNLOADED } from './ipc-channels';
 
-export type UpdateChannel = 'stable' | 'rc' | 'beta' | 'alpha';
+export type UpdateChannel = 'stable' | 'rc' | 'beta' | 'alpha' | 'nightly';
 
 export type UpdateStatus =
     | { status: 'unsupported'; platform: 'linux' }

src/renderer/screen.js

@@ -1873,7 +1873,7 @@ window.__feedBackDesktopAudioHooks = window.__feedBackDesktopAudioHooks || {};
         const linuxNote = document.getElementById('update-linux-note');
         if (!channelSelect || !checkBtn || !statusEl) return;
 
-        const VALID_CHANNELS = ['stable', 'rc', 'beta', 'alpha'];
+        const VALID_CHANNELS = ['stable', 'rc', 'beta', 'alpha', 'nightly'];
         const storedChannelRaw = localStorage.getItem('slopsmith-update-channel');
         const storedChannel = VALID_CHANNELS.includes(storedChannelRaw) ? storedChannelRaw : 'stable';
         channelSelect.value = storedChannel;

src/renderer/settings.html

@@ -9,8 +9,9 @@
                     <option value="rc">Release candidate</option>
                     <option value="beta">Beta</option>
                     <option value="alpha">Alpha</option>
+                    <option value="nightly">Nightly</option>
                 </select>
-                <p class="text-xs text-slate-500 mt-1">Pre-release channels (alpha/beta/rc) opt you into early builds.</p>
+                <p class="text-xs text-slate-500 mt-1">Pre-release channels (rc/beta/alpha) opt you into early builds. Nightly rebuilds from the latest code every night and is the least stable.</p>
             </div>
             <div class="flex flex-col">
                 <label class="block text-xs text-slate-400 mb-1">Manual check</label>