feat(cliproxy): pool onboarding hints for existing multi-profile users

- ccs doctor, native account launch, and ccs auth create now surface a
  one-line pool suggestion when >=2 native Claude profiles exist and no
  pool is enabled; shared once-per-install dismissal; TTY-gated; hint
  failures can never break a launch (guarded, single config read)
- credential import from native profiles evaluated and REJECTED:
  refresh tokens are client_id-bound and not replayable cross-client;
  pool setup requires fresh OAuth per account (verdict report in plan)

Part of #1464 account pools (phase 5).

src/auth/commands/create-command.ts

@@ -29,7 +29,11 @@ import { exitWithError } from '../../errors';
 import { ExitCode } from '../../errors/exit-codes';
 import { CommandContext, parseArgs, rejectUnsupportedAuthOptions } from './types';
 import { stripAmbientProviderCredentials } from './create-command-env';
-import { isUnifiedMode } from '../../config/config-loader-facade';
+import { isUnifiedMode, hasUnifiedConfig } from '../../config/config-loader-facade';
+import {
+  maybeShowPoolOnboardingHint,
+  countNativeClaudeProfiles,
+} from '../../cliproxy/routing/pool-onboarding-hint';
 
 function sanitizeProfileNameForInstance(name: string): string {
   return name.replace(/[^a-zA-Z0-9_-]/g, '-').toLowerCase();
@@ -185,6 +189,18 @@ export async function handleCreate(ctx: CommandContext, args: string[]): Promise
     }
   };
 
+  // Pool suggestion: when creating a 2nd+ native Claude profile, show the
+  // once-per-install onboarding hint.  Print-only, TTY-gated, never blocks.
+  // Pass existingCount + 1 so the hint sees the post-create count (>= 2).
+  // Gated on hasUnifiedConfig() so legacy profiles.json-only installs receive
+  // the hint from ccs doctor only (where dismissal semantics are preserved).
+  if (!profileExistedBeforeCreate && hasUnifiedConfig()) {
+    const existingCount = countNativeClaudeProfiles();
+    if (existingCount >= 1) {
+      maybeShowPoolOnboardingHint(existingCount + 1);
+    }
+  }
+
   try {
     // Create instance directory
     console.log(info(`Creating profile: ${profileName}`));