feat: add shared call-time isConductor() helper

Single source of truth for Conductor host detection in TS consumers
(CONDUCTOR_WORKSPACE_PATH / CONDUCTOR_PORT). Reads the passed env at
call time, not a module-load snapshot, so unit tests can pin the env
inline without Bun --preload (esm-hoist-breaks-env-pin-bootstrap).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/is-conductor.ts

@@ -0,0 +1,19 @@
+/**
+ * Conductor host detection — single source of truth for TS consumers.
+ *
+ * Conductor (the Mac app that runs many coding agents in parallel) sets
+ * CONDUCTOR_WORKSPACE_PATH / CONDUCTOR_PORT in the session env. The same two
+ * vars are what `bin/gstack-session-kind` keys on (it collapses Conductor into
+ * `interactive`, so it can't be reused to distinguish Conductor specifically —
+ * hence this dedicated helper).
+ *
+ * IMPORTANT: detection is a CALL-TIME read of the passed-in env (default
+ * `process.env`), never a module-load-time snapshot. ESM hoists static imports
+ * above any in-file `process.env.X = ...`, so a load-time read can't be pinned
+ * by a test without Bun --preload. Reading at call time lets unit tests set
+ * `process.env.CONDUCTOR_WORKSPACE_PATH` inline before invoking. See the
+ * `esm-hoist-breaks-env-pin-bootstrap` learning.
+ */
+export function isConductor(env: NodeJS.ProcessEnv = process.env): boolean {
+  return !!(env.CONDUCTOR_WORKSPACE_PATH || env.CONDUCTOR_PORT);
+}

test/is-conductor.test.ts

@@ -0,0 +1,50 @@
+import { describe, test, expect } from 'bun:test';
+import { isConductor } from '../lib/is-conductor';
+
+describe('is-conductor', () => {
+  test('true when CONDUCTOR_WORKSPACE_PATH is set', () => {
+    expect(isConductor({ CONDUCTOR_WORKSPACE_PATH: '/Users/x/conductor/ws' })).toBe(true);
+  });
+
+  test('true when CONDUCTOR_PORT is set', () => {
+    expect(isConductor({ CONDUCTOR_PORT: '55070' })).toBe(true);
+  });
+
+  test('true when both are set', () => {
+    expect(isConductor({ CONDUCTOR_WORKSPACE_PATH: '/ws', CONDUCTOR_PORT: '55070' })).toBe(true);
+  });
+
+  test('false when neither is set', () => {
+    expect(isConductor({ HOME: '/Users/x', PATH: '/usr/bin' })).toBe(false);
+  });
+
+  test('false on an empty env', () => {
+    expect(isConductor({})).toBe(false);
+  });
+
+  test('false when the vars are present but empty (Codex #1 hardening — empty != set)', () => {
+    expect(isConductor({ CONDUCTOR_WORKSPACE_PATH: '', CONDUCTOR_PORT: '' })).toBe(false);
+  });
+
+  test('reads the passed env at call time, not a module-load snapshot', () => {
+    const env: NodeJS.ProcessEnv = {};
+    expect(isConductor(env)).toBe(false);
+    // mutate AFTER the first call — a call-time read must see the new value
+    env.CONDUCTOR_PORT = '55070';
+    expect(isConductor(env)).toBe(true);
+  });
+
+  test('defaults to process.env when no arg is passed', () => {
+    const saved = process.env.CONDUCTOR_PORT;
+    try {
+      process.env.CONDUCTOR_PORT = '12345';
+      expect(isConductor()).toBe(true);
+      delete process.env.CONDUCTOR_PORT;
+      // CONDUCTOR_WORKSPACE_PATH may be set in a real Conductor session; guard the assertion
+      if (!process.env.CONDUCTOR_WORKSPACE_PATH) expect(isConductor()).toBe(false);
+    } finally {
+      if (saved === undefined) delete process.env.CONDUCTOR_PORT;
+      else process.env.CONDUCTOR_PORT = saved;
+    }
+  });
+});