fix(lattice): compile durable fragment tombstones

[mgazza]

Summary

• keep the existing feat(lattice): add invalidatable auto-config compiler #4321/feat(lattice): publish durable compiled config #4326/feat(lattice): add fragment adapter registry #4328 compiler/publication/registry stack as the single coordinator
• translate only a durable integration removal into a deterministic empty compiler fragment
• acknowledge and publish the removed generation while clearing that provider's prior contribution
• preserve public adapter reads and transient-OFFLINE last-known-good behavior

Why

DurableFragmentAdapter.read_snapshot() intentionally fails closed after removal. The sealed
registry therefore persisted the removal invalidation but could not observe/acknowledge its
generation. A second coordinator was prototyped and rejected in review because it duplicated
existing restart, CAS, OFFLINE and superseded-candidate state machines.

This patch changes only the registry's private compiler-reader binding. Live states return the
exact original snapshot; durable tombstones become a schema-valid empty fragment at the same
provider/generation. Public read_snapshot() and registry.readers remain unchanged.

Safety

• registry remains default-off and unregistered
• no ProviderSnapshot, compile_auto_config, LatticeAutoConfigCompiler, or
  CompiledLatticeCompiler changes
• explicit removal has no nodes, relationships, aliases, identities, roles, config projections,
  capabilities, or authority
• transient OFFLINE still follows the existing active-provider-unavailable LKG guard
• every fresh structural state revalidates provider, generation, snapshot, and semantic fingerprint
• same-generation resurrection remains rejected
• invalidation during compilation retains the existing bounded follow-up/superseded-candidate logic

Validation

• 148 relevant tests pass on Python 3.9 and Python 3.14
• full pre-commit hooks pass
• independent request-changes/fix/re-review: approved
• GitNexus staged analysis: LOW, zero affected processes

Train

• base: feat: add Fox cloud lattice fragment publisher #4339
• tracking: Predictive-Cloud-Ltd/predbat-saas-infra#561 and Update bug_report.md #466