Inspect validated XMD artifacts through workflow status and history

[taras]

Delivered baseline

Closed by PR #619, head 7e20474bd002490ebe208ed323f68f87a7d9e9cf, merge commit 68e5f8065755daf3d4222a70a331fae183eff350, as part of #599.

This issue delivered provider-neutral WorkflowArtifactSnapshot / WorkflowArtifactHistory, inspectArtifact / historyArtifact, shared inspection/history projection, source-discriminated status/history grammar, complete verification before projection, path-independent JSON, read-only sidecar-free behavior, retained-run parity, list exclusion, and focused I1–I5 regressions.

The retained contracts are:

• Complete manifest recognition precedes any status/history/forkability result.
• Inspection executes no document, acquires no executor lock, materializes no Workspace, fetches no definition, contacts no provider, and creates no retained state or sidecar.
• The same artifact produces the same semantic output independent of path or installed adapters.
• Exactly one retained-run or artifact source is accepted; list remains retained-run discovery only.

Agent-aware amendment

#623 adds intrinsic Agent forkability from sealed bundle/token/unavailable evidence. It preserves all contracts above, never displays bundle bytes or checkpoint tokens, and never consults destination adapter support. Only artifact-backed fork performs destination capability checks.

This issue remains closed; #623 is the blocking amendment issue. Approved plan: b42339b3d6df869d65e4b34a8ba89f60728f8a58.