resolve_reverse_segment degrades silently on two DB errors, producing a false 'broken path' rejection for a legitimate inherited reverse relationship #2885

Context

Surfaced by a codebase scan focused on the extends-chain/ADR-078 bug class. Related to (but distinct from) core#2885 (validate_play's own-hop error-blame issue).

Problem

resolve_reverse_segment (packages/core/src/playbook/validation.rs:739-763) has two silent-degradation points:

• resolve_type_chain(...).unwrap_or_else(|_| vec![node_type]) collapses the ancestor chain to just the concrete type on error.
• get_inbound_relationships's Err case does continue, skipping that candidate silently.

Either failure makes a legitimate inherited reverse relationship name (e.g. node.blocked_by declared on an ancestor, used on a subtype instance) resolve to None. The caller then reports this as a broken path, blaming the user's expression for a transient DB error — no log, no degraded_reasons entry, nothing to distinguish it from a genuine typo.

Suggested approach

Same pattern as the other validation.rs findings from this scan (core#2885): propagate the error instead of silently degrading to a possibly-wrong answer, or at minimum log loudly and/or surface it distinctly from a real "not found."