[P1] Introduce canonical ObjectKey and ambiguity-safe object resolution

[jackyclever]

CLI/Core scope

Use one qualified identity contract across discovery, methods, source, relations, extensions, references, and future generation.

Split from Aether #7. Aether remains responsible for retaining and validating the resolved identity across a reasoning workflow.

Current problem

Name-only lookup and first-row/default-kind behavior are unsafe where Microsoft, ISV, and customer packages contain overlapping object names or kinds.

Acceptance criteria

• Define a stable ObjectKey = { objectType, package, model, name }.
• Discovery returns all qualified candidates and preserves original casing.
• Final resolution follows D365FO case semantics without discarding package/model identity.
• Ambiguity returns a structured candidate list; never silently select the first row or default kind.
• Method, source, relation, extension, reference, and generation queries accept and return the same ObjectKey.
• Inheritance and extension target resolution preserve identity at each hop.
• Tests cover same names across types/models/packages, casing variants, missing objects, and stale indexes.