feat(cli): wire active extension context into slash command routing

Extracts the extension context from slash commands based on their registered metadata and sets it as the active context in the Config before execution. This enables the backend to dynamically route plan directories based on the extension that owns the invoked command.

packages/cli/src/ui/AppContainer.tsx

@@ -1308,6 +1308,17 @@ Logging in with Google... Restarting Gemini CLI to continue.
         }
       }
 
+      const parsedCommand = parseSlashCommand(
+        submittedValue,
+        slashCommands ?? [],
+      );
+
+      if (parsedCommand.extensionContext && config) {
+        if (config.hasExtensionPlanDir(parsedCommand.extensionContext)) {
+          config.setActiveExtensionContext(parsedCommand.extensionContext);
+        }
+      }
+
       const isSlash = isSlashCommand(submittedValue.trim());
       const isIdle = streamingState === StreamingState.Idle;
       const isAgentRunning =
@@ -1315,10 +1326,7 @@ Logging in with Google... Restarting Gemini CLI to continue.
         isToolExecuting(pendingHistoryItems);
 
       if (isSlash && isAgentRunning) {
-        const { commandToExecute } = parseSlashCommand(
-          submittedValue,
-          slashCommands ?? [],
-        );
+        const commandToExecute = parsedCommand.commandToExecute;
         if (commandToExecute?.isSafeConcurrent) {
           void handleSlashCommand(submittedValue);
           addInput(submittedValue);

packages/cli/src/ui/commands/clearCommand.test.ts

@@ -45,6 +45,7 @@ describe('clearCommand', () => {
               fireSessionEndEvent: vi.fn().mockResolvedValue(undefined),
               fireSessionStartEvent: vi.fn().mockResolvedValue(undefined),
             }),
+            setActiveExtensionContext: vi.fn(),
             injectionService: {
               clear: mockHintClear,
             },

packages/cli/src/ui/commands/clearCommand.ts

@@ -30,8 +30,9 @@ export const clearCommand: SlashCommand = {
       await hookSystem.fireSessionEndEvent(SessionEndReason.Clear);
     }
 
-    // Reset user steering hints
+    // Reset user steering hints and extension context
     config?.injectionService.clear();
+    config?.setActiveExtensionContext(undefined);
 
     // Start a new conversation recording with a new session ID
     // We MUST do this before calling resetChat() so the new ChatRecordingService