feat(02-03): create context IPC handler and channel constants

- Add CONTEXT_LIST, CONTEXT_GET_ACTIVE, CONTEXT_SWITCH, CONTEXT_CHANGED channel constants
- Create context.ts IPC handler module with list, getActive, and switch operations
- Update handlers.ts to accept onContextSwitched callback and register context handlers
- Pass onContextSwitched from main index.ts to IPC initialization
- Context switching triggers onContextSwitched callback for event re-wiring

src/main/index.ts

@@ -154,7 +154,7 @@ function initializeServices(): void {
   updaterService = new UpdaterService();
 
   // Initialize IPC handlers with registry
-  initializeIpcHandlers(contextRegistry, updaterService, sshConnectionManager);
+  initializeIpcHandlers(contextRegistry, updaterService, sshConnectionManager, onContextSwitched);
 
   // Forward SSH state changes to renderer
   sshConnectionManager.on('state-change', (status: unknown) => {

src/main/ipc/context.ts

@@ -0,0 +1,97 @@
+/**
+ * Context IPC Handlers - Manages context switching and listing.
+ *
+ * Channels:
+ * - context:list - List all available contexts (local + SSH)
+ * - context:getActive - Get current active context ID
+ * - context:switch - Switch to a different context
+ */
+
+import {
+  CONTEXT_CHANGED,
+  CONTEXT_GET_ACTIVE,
+  CONTEXT_LIST,
+  CONTEXT_SWITCH,
+} from '@preload/constants/ipcChannels';
+import { createLogger } from '@shared/utils/logger';
+
+import type { ServiceContext, ServiceContextRegistry } from '../services';
+import type { IpcMain } from 'electron';
+
+const logger = createLogger('IPC:context');
+
+// =============================================================================
+// Module State
+// =============================================================================
+
+let registry: ServiceContextRegistry;
+let onContextSwitched: (context: ServiceContext) => void;
+
+// =============================================================================
+// Initialization
+// =============================================================================
+
+/**
+ * Initialize context handlers with required services.
+ * @param contextRegistry - The service context registry
+ * @param onSwitched - Callback to invoke after successful context switch
+ */
+export function initializeContextHandlers(
+  contextRegistry: ServiceContextRegistry,
+  onSwitched: (context: ServiceContext) => void
+): void {
+  registry = contextRegistry;
+  onContextSwitched = onSwitched;
+}
+
+// =============================================================================
+// Handler Registration
+// =============================================================================
+
+export function registerContextHandlers(ipcMain: IpcMain): void {
+  ipcMain.handle(CONTEXT_LIST, async () => {
+    try {
+      const contexts = registry.list();
+      return { success: true, data: contexts };
+    } catch (err) {
+      const message = err instanceof Error ? err.message : String(err);
+      logger.error('Failed to list contexts:', message);
+      return { success: false, error: message };
+    }
+  });
+
+  ipcMain.handle(CONTEXT_GET_ACTIVE, async () => {
+    try {
+      const activeContextId = registry.getActiveContextId();
+      return { success: true, data: activeContextId };
+    } catch (err) {
+      const message = err instanceof Error ? err.message : String(err);
+      logger.error('Failed to get active context:', message);
+      return { success: false, error: message };
+    }
+  });
+
+  ipcMain.handle(CONTEXT_SWITCH, async (_event, contextId: string) => {
+    try {
+      // Switch to the new context
+      const { current } = registry.switch(contextId);
+
+      // Invoke the context switched callback (re-wires file watcher events)
+      onContextSwitched(current);
+
+      return { success: true, data: { contextId } };
+    } catch (err) {
+      const message = err instanceof Error ? err.message : String(err);
+      logger.error(`Context switch to "${contextId}" failed:`, message);
+      return { success: false, error: message };
+    }
+  });
+
+  logger.info('Context handlers registered');
+}
+
+export function removeContextHandlers(ipcMain: IpcMain): void {
+  ipcMain.removeHandler(CONTEXT_LIST);
+  ipcMain.removeHandler(CONTEXT_GET_ACTIVE);
+  ipcMain.removeHandler(CONTEXT_SWITCH);
+}

src/main/ipc/handlers.ts

@@ -17,6 +17,11 @@ import { createLogger } from '@shared/utils/logger';
 import { ipcMain } from 'electron';
 
 import { registerConfigHandlers, removeConfigHandlers } from './config';
+import {
+  initializeContextHandlers,
+  registerContextHandlers,
+  removeContextHandlers,
+} from './context';
 
 const logger = createLogger('IPC:handlers');
 import { registerNotificationHandlers, removeNotificationHandlers } from './notifications';
@@ -45,7 +50,12 @@ import {
 import { registerUtilityHandlers, removeUtilityHandlers } from './utility';
 import { registerValidationHandlers, removeValidationHandlers } from './validation';
 
-import type { ServiceContextRegistry, SshConnectionManager, UpdaterService } from '../services';
+import type {
+  ServiceContext,
+  ServiceContextRegistry,
+  SshConnectionManager,
+  UpdaterService,
+} from '../services';
 
 /**
  * Initializes IPC handlers with service registry.
@@ -53,7 +63,8 @@ import type { ServiceContextRegistry, SshConnectionManager, UpdaterService } fro
 export function initializeIpcHandlers(
   registry: ServiceContextRegistry,
   updater: UpdaterService,
-  sshManager: SshConnectionManager
+  sshManager: SshConnectionManager,
+  onContextSwitched: (context: ServiceContext) => void
 ): void {
   // Initialize domain handlers with registry
   initializeProjectHandlers(registry);
@@ -62,6 +73,7 @@ export function initializeIpcHandlers(
   initializeSubagentHandlers(registry);
   initializeUpdaterHandlers(updater);
   initializeSshHandlers(sshManager, registry);
+  initializeContextHandlers(registry, onContextSwitched);
 
   // Register all handlers
   registerProjectHandlers(ipcMain);
@@ -74,6 +86,7 @@ export function initializeIpcHandlers(
   registerConfigHandlers(ipcMain);
   registerUpdaterHandlers(ipcMain);
   registerSshHandlers(ipcMain);
+  registerContextHandlers(ipcMain);
 
   logger.info('All handlers registered');
 }
@@ -93,6 +106,7 @@ export function removeIpcHandlers(): void {
   removeConfigHandlers(ipcMain);
   removeUpdaterHandlers(ipcMain);
   removeSshHandlers(ipcMain);
+  removeContextHandlers(ipcMain);
 
   logger.info('All handlers removed');
 }

src/preload/constants/ipcChannels.ts

@@ -105,3 +105,19 @@ export const UPDATER_INSTALL = 'updater:install';
 
 /** Status event channel (main -> renderer) */
 export const UPDATER_STATUS = 'updater:status';
+
+// =============================================================================
+// Context API Channels
+// =============================================================================
+
+/** List all available contexts (local + SSH) */
+export const CONTEXT_LIST = 'context:list';
+
+/** Get active context ID */
+export const CONTEXT_GET_ACTIVE = 'context:getActive';
+
+/** Switch to a different context */
+export const CONTEXT_SWITCH = 'context:switch';
+
+/** Context changed event channel (main -> renderer) */
+export const CONTEXT_CHANGED = 'context:changed';