# Context
`yarn twenty plan` fails when the app has never been installed in the
target workspace:
```
Sync failed with error: Application "f5ce204f-..." is not installed in workspace "10f39a9d-...". Install it first.
Hint: run `yarn twenty dev --once` to register the app in this workspace, then retry.
```
This forces developers to apply before they can plan, which defeats the
purpose of `plan`. Planning a not-yet-installed app is well defined: the
from-state is empty, so the plan is simply "create everything".
## Why it failed
The dry-run sync required the application row to exist in two places:
1. `ApplicationSyncService.synchronizeFromManifest` threw
`APP_NOT_INSTALLED` when the app row was missing, because the dry-run
needs an owner `FlatApplication` to anchor the from → to metadata diff.
2.
`WorkspaceMigrationFlatEntityMapsService.computeAllInvolvedApplicationIds`
threw when the owner app id was absent from `flatApplicationMaps`, even
though the only hard dependency of a build is the twenty standard
application.
`apply` never hit this because it registers the app row as a side effect
before syncing (and even swallows this exact error on its pre-apply
plan).
# What this PR does
Keeps `plan` strictly read-only, no registration or app row is created:
- **`application-sync.service.ts`**: on dry-run, resolve the owner to
the installed application when it exists (unchanged behavior), otherwise
build a virtual, non-persisted `FlatApplication` from the manifest. Its
freshly generated id matches no existing metadata, so the from-state
slice resolves to empty and every manifest entity shows up as a create.
- **`workspace-migration-flat-entity-maps.service.ts`**: relax the guard
so only the twenty standard application is required. A missing owner app
just contributes an empty from-slice instead of throwing. Installed apps
take the exact same path as before (`applicationId` defined → identical
behavior).
Weiko
666ceb41d5