RunConfig is read from disk multiple times per workload during reconciliation

Problem

During a single reconciliation cycle (e.g., thv list or thv status), the fileStatusManager reads the same RunConfig file from disk multiple times per workload via runConfigStore.GetReader():

1. isRemoteWorkload() — reads remote_url field
2. isOwnedByActiveRuntime() — reads runtime_name field
3. migrateRuntimeName() — reads all fields (for write-back on legacy workloads)

Each call opens the file, parses JSON, extracts one or two fields, then closes. For a user with N workloads, thv list performs up to 3N file reads where N would suffice.

References

• isRemoteWorkload: pkg/workloads/statuses/file_status.go (~line 169)
• isOwnedByActiveRuntime: pkg/workloads/statuses/file_status.go (~line 82)
• migrateRuntimeName: pkg/workloads/statuses/file_status.go (~line 114)
• Related import cycle TODO: pkg/workloads/statuses/file_status.go (~line 73)

Introduced by #4434.

Start in pkg/workloads/statuses/file_status.go, reading isOwnedByActiveRuntime(), migrateRuntimeName(), and isRemoteWorkload(), then trace the reconciliation paths used by thv list and thv status. Consolidate the per-workload RunConfig access while preserving the existing status and migration behavior; done means one disk read per workload instead of repeated reads.