fix(cli): auto-detect existing agent files in migration without modifying selectAgentTargetPaths

Revert changes to selectAgentTargetPaths and instead apply the same
auto-detection pattern already used in create/bin.ts to migration/bin.ts.
This skips the agent selector prompt when agent files exist, while
preserving the full conflict resolution and content update flow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: zerone0x

packages/cli/src/migration/bin.ts

@@ -14,6 +14,7 @@ import {
 } from '../types/index.js';
 import {
   detectAgentConflicts,
+  detectExistingAgentTargetPaths,
   selectAgentTargetPaths,
   writeAgentInstructions,
 } from '../utils/agent.js';
@@ -339,13 +340,19 @@ async function collectMigrationPlan(
     }
   }
 
-  // 3. Agent selection
-  const selectedAgentTargetPaths = await selectAgentTargetPaths({
-    interactive: options.interactive,
-    agent: options.agent,
-    projectRoot: rootDir,
-    onCancel: () => cancelAndExit(),
-  });
+  // 3. Agent selection (auto-detect existing agent files to skip the selector prompt)
+  const existingAgentTargetPaths =
+    options.agent !== undefined || !options.interactive
+      ? undefined
+      : detectExistingAgentTargetPaths(rootDir);
+  const selectedAgentTargetPaths =
+    existingAgentTargetPaths !== undefined
+      ? existingAgentTargetPaths
+      : await selectAgentTargetPaths({
+          interactive: options.interactive,
+          agent: options.agent,
+          onCancel: () => cancelAndExit(),
+        });
 
   // 4. Agent conflict detection + prompting
   const agentConflicts = await detectAgentConflicts({

packages/cli/src/utils/agent.ts

@@ -196,27 +196,17 @@ const AGENT_INSTRUCTIONS_END_MARKER = '<!--VITE PLUS END-->';
 export async function selectAgentTargetPaths({
   interactive,
   agent,
-  projectRoot,
   onCancel,
 }: {
   interactive: boolean;
   agent?: AgentSelection;
-  projectRoot?: string;
   onCancel: () => void;
 }) {
   // Skip entirely if --no-agent is passed
   if (agent === false) {
     return undefined;
   }
 
-  // If agent files already exist in the project, reuse them instead of prompting
-  if (interactive && !agent && projectRoot) {
-    const existingPaths = detectExistingAgentTargetPaths(projectRoot);
-    if (existingPaths) {
-      return existingPaths;
-    }
-  }
-
   if (interactive && !agent) {
     const selectedAgents = await prompts.multiselect({
       message: 'Which agents are you using?',