ADC-684: fail closed on unowned runtime actions

[wolf75222]

Scope

Corrective, source-only ADC-684 slice stacked on #631. It deliberately avoids ADC-683 communicator/FieldView work and ADC-685 ConsumerGraph publication semantics.

The existing RuntimePlan authentication and mono/multi-layout projections still allowed some derived action classes to reach installation as advisory metadata even though no native executor owned them. A single-layout halo was layout-qualified, but its derived depth was not checked against the exact compiled block ghost allocation.

Changes

• map every planned single-layout halo back through its RuntimeCall and block assignment;
• require its depth to fit the authenticated compiled spatial ghost allocation;
• reject duplicate/missing halo owners and mismatched compiled block sets before engine construction;
• fail closed before native fact probing when buffer allocations, cross-memory fences, or clock joins have no native execution owner;
• leave ConsumerGraph collectives with their existing distinct transactional owner;
• document the ownership boundary and add focused negative tests.

Source-only validation

• 16 targeted runtime planning/install tests passed;
• Python compileall passed;
• Ruff passed;
• docs/check_docs.py passed (one pre-existing final-spec freshness warning);
• git diff --check passed.

The broader two-file pytest attempt was not a native validation: this isolated worktree intentionally has no locally built pops._pops, so native-fixture cases stopped at ImportError. No shared install or native build was used to hide that limitation.

Explicit non-proofs

This does not complete ADC-684. It makes unsupported action classes fail closed; it does not implement a native buffer allocator, cross-memory fence scheduler, or clock-join scheduler. Multi-layout halos remain explicitly unsupported pending a per-layout scheduler. No installed-package, CTest, MPI, GPU/device, bit-identical cross-rank, or end-to-end heterogeneous runtime campaign was executed here. ADC-683, ADC-685, the M4 gate, and their stacked P3 dependencies remain separate prerequisites.