fix: e2e/integration test infrastructure and Makefile test targets

- Fix make test: was pointing to non-existent api/tests/, now runs unit tests
  correctly with --ignore=e2e --ignore=integration
- Remove dead phase test targets (test-phase1..4, test-all-phases) that all
  referenced cd api && pytest tests/ (non-existent path)
- Add .test_admin_pass file: reset_admin_password.py now writes a persistent
  test password file alongside .admin_initial_password; the API never deletes
  it (unlike .admin_initial_password which is consumed on first startup)
- Update both integration/conftest.py and e2e/helpers/admin_password.py to
  read .test_admin_pass before .admin_initial_password — so tests work after
  make restart without needing PIC_ADMIN_PASS env var
- Add AI collaboration rules to CLAUDE.md (auto-loaded every session)

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

scripts/reset_admin_password.py

@@ -15,6 +15,7 @@ sys.path.insert(0, os.path.join(os.path.dirname(__file__), '..', 'api'))
 
 ROOT = os.path.join(os.path.dirname(__file__), '..')
 INIT_PW_FILE = os.path.normpath(os.path.join(ROOT, 'data', 'api', '.admin_initial_password'))
+TEST_PW_FILE  = os.path.normpath(os.path.join(ROOT, 'data', 'api', '.test_admin_pass'))
 
 
 def _generate_password(length: int = 20) -> str:
@@ -88,13 +89,19 @@ def main() -> None:
 
     _set_password(password)
 
-    # Also update the initial password file so show-admin-password works
+    # Write the initial password file (API reads it on first start, then deletes it)
     os.makedirs(os.path.dirname(INIT_PW_FILE), exist_ok=True)
     with open(INIT_PW_FILE, 'w') as f:
         f.write(password)
 
+    # Write the persistent test password file (never deleted by the API)
+    with open(TEST_PW_FILE, 'w') as f:
+        f.write(password)
+    os.chmod(TEST_PW_FILE, 0o600)
+
     _print_banner(password)
     print(f'\n  Also saved to: {INIT_PW_FILE}')
+    print(f'  Test file:     {TEST_PW_FILE}  (persists across API restarts)')
     print('  Restart the API container for the change to take effect:')
     print('    docker restart cell-api')