feat: system settings tab — launch at login and prevent-sleep toggles

AppSettings.system persisted through the existing settings IPC; the main
process applies real side effects at startup and on every save via
app.setLoginItemSettings and powerSaveBlocker.

src/main/settingsStore.ts

@@ -1,4 +1,4 @@
-import { app, ipcMain } from 'electron'
+import { app, ipcMain, powerSaveBlocker } from 'electron'
 import { mkdirSync, readFileSync, renameSync, writeFileSync } from 'fs'
 import { join } from 'path'
 import { Ipc } from '../shared/ipc'
@@ -7,6 +7,7 @@ import {
   DEFAULT_SETTINGS,
   type AppSettings,
   type HighlightRule,
+  type SystemSettings,
   type TerminalSettings
 } from '../shared/settings'
 import type { TerminalTheme } from '../shared/theme'
@@ -14,6 +15,8 @@ import { broadcast } from './broadcast'
 
 const settingsPath = (): string => join(app.getPath('userData'), 'settings.json')
 
+const DEFAULT_SYSTEM: SystemSettings = { launchAtLogin: false, preventSleep: false }
+
 const TERMINAL_KEYS = new Set(Object.keys(DEFAULT_SETTINGS.terminal) as (keyof TerminalSettings)[])
 
 /** Light structural check for a persisted highlight rule. */
@@ -66,9 +69,53 @@ function deepMerge(raw: unknown): { settings: AppSettings; errors: string[] } {
     }
   }
 
+  let system: unknown = DEFAULT_SYSTEM
+  if (raw !== null && typeof raw === 'object') {
+    const sys = (raw as { system?: unknown }).system
+    if (sys !== null && typeof sys === 'object') {
+      const candidate = sys as Record<string, unknown>
+      system = {
+        launchAtLogin: candidate.launchAtLogin === true,
+        preventSleep: candidate.preventSleep === true
+      }
+    }
+  }
+
   const themes: TerminalTheme[] = Array.isArray(customThemes) ? (customThemes as TerminalTheme[]) : []
 
-  return { settings: { terminal, customThemes: themes, highlightRules: sanitizeRules(highlightRules) }, errors }
+  return {
+    settings: {
+      terminal,
+      customThemes: themes,
+      highlightRules: sanitizeRules(highlightRules),
+      system: system as SystemSettings
+    },
+    errors
+  }
+}
+
+// ---- real system side effects ------------------------------------------------
+
+let sleepBlockerId: number | undefined
+
+/** Apply OS-level effects of the system settings (login item, sleep blocker). */
+function applySystemSettings(system: SystemSettings): void {
+  try {
+    app.setLoginItemSettings({ openAtLogin: system.launchAtLogin })
+  } catch (err) {
+    console.error('[settings] setLoginItemSettings failed', err)
+  }
+  if (system.preventSleep && sleepBlockerId === undefined) {
+    sleepBlockerId = powerSaveBlocker.start('prevent-app-suspension')
+  } else if (!system.preventSleep && sleepBlockerId !== undefined) {
+    powerSaveBlocker.stop(sleepBlockerId)
+    sleepBlockerId = undefined
+  }
+}
+
+/** Apply system side effects for the settings loaded at startup. */
+export function applyStartupSystemSettings(settings: AppSettings): void {
+  applySystemSettings(settings.system)
 }
 
 export function loadSettings(): AppSettings {
@@ -80,7 +127,8 @@ export function loadSettings(): AppSettings {
     return {
       terminal: { ...DEFAULT_SETTINGS.terminal },
       customThemes: [...DEFAULT_SETTINGS.customThemes],
-      highlightRules: DEFAULT_HIGHLIGHT_RULES.map((rule) => ({ ...rule }))
+      highlightRules: DEFAULT_HIGHLIGHT_RULES.map((rule) => ({ ...rule })),
+      system: { ...DEFAULT_SYSTEM }
     }
   }
 }
@@ -89,8 +137,10 @@ export function saveSettings(next: AppSettings): AppSettings {
   const merged = deepMerge({
     terminal: next.terminal,
     customThemes: next.customThemes,
-    highlightRules: next.highlightRules
+    highlightRules: next.highlightRules,
+    system: next.system ?? DEFAULT_SYSTEM
   }).settings
+  applySystemSettings(merged.system)
   const pretty = JSON.stringify(merged, null, 2)
 
   mkdirSync(app.getPath('userData'), { recursive: true })