fix: restore ENABLE_S6_IMAGE default-true logic broken by || true

The expression `getEnvironmentVariable('ENABLE_S6_IMAGE') === 'true' || true`
always evaluates to `true`, ignoring the env var entirely. CI sets
`ENABLE_S6_IMAGE=false` for tests that need non-S6 images, so they were
getting S6 images anyway, causing 'container not found (root-container)'
and 'chown: cannot access extract-platform.sh' failures.

Restore the correct logic: default to true (S6 images) but honour
`ENABLE_S6_IMAGE=false` to opt out.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Jeffrey Tang <jeffrey@swirldslabs.com>

Author: JeffreyDallas

src/core/constants.ts

@@ -48,7 +48,7 @@ export const KIND_NODE_IMAGE: string =
 
 export const PODMAN_MACHINE_NAME: string = 'podman-machine-default';
 export const SOLO_DEV_OUTPUT: boolean = Boolean(getEnvironmentVariable('SOLO_DEV_OUTPUT')) || false;
-export const ENABLE_S6_IMAGE: boolean = getEnvironmentVariable('ENABLE_S6_IMAGE') === 'true' || true;
+export const ENABLE_S6_IMAGE: boolean = getEnvironmentVariable('ENABLE_S6_IMAGE') !== 'false';
 
 export const ROOT_CONTAINER: ContainerName = ContainerName.of('root-container');
 export const SOLO_REMOTE_CONFIGMAP_NAME: string = 'solo-remote-config';