fix: preserve signup flags in classic mode

resolveMode classifies a TTY classic run as 'interactive', causing
buildSession to strip --auth-onboarding / --email / --accept-tos.
Classic mode is interactive-but-not-TUI: it uses terminal prompts,
not the Ink screens that own those decisions, and explicitly supports
direct signup via CLI flags (runDirectSignupIfRequested in default.ts).

Detect --classic / AMPLITUDE_WIZARD_CLASSIC=1 in buildSessionFromOptions
and omit executionMode so buildSession honors the flags.

Author: cursoragent

src/commands/helpers.ts

@@ -101,6 +101,15 @@ export const buildSessionFromOptions = async (
     agent: Boolean(options.agent),
     isTTY: Boolean(process.stdout.isTTY),
   });
+  // Classic mode is interactive-but-not-TUI: it uses terminal prompts, not
+  // the Ink screens that own signup-flag decisions. `resolveMode` has no
+  // knowledge of `--classic`, so a TTY classic run lands on `interactive`
+  // and `buildSession` would strip `--auth-onboarding` / `--email` /
+  // `--accept-tos`, breaking classic's direct-signup path. Omit
+  // `executionMode` for classic so buildSession honors the flags as today.
+  const isClassic =
+    Boolean(options.classic) || process.env.AMPLITUDE_WIZARD_CLASSIC === '1';
+  const effectiveMode = isClassic ? undefined : mode;
   const session = buildSession({
     debug: options.debug as boolean | undefined,
     verbose: options.verbose as boolean | undefined,
@@ -128,7 +137,7 @@ export const buildSessionFromOptions = async (
     // refers to the Amplitude project (formerly workspace), not the app.
     appId: options.appId as string | undefined,
     appName: options.appName as string | undefined,
-    executionMode: mode,
+    executionMode: effectiveMode,
   });
   bootstrapInstallDir(session.installDir);
   return session;