Make lineage equivalence levels and comparison coverage explicit

[jacksenpierce]

Status

Confirmed as a design/contract gap in Parmesan 3.0.2. This issue does not assume that every kind of equivalence must be collapsed into one fingerprint.

Observed behavior

Semantic snapshots fingerprint current nodes (including revision UUIDs), graphs, triples, and tags. The lineage comparator currently compares node content hashes only. Registered extension schemas receive drift checks, but extension contents, custom views, and triggers do not participate in the semantic snapshot fingerprint.

Desired outcome

Return explicit, separately named comparison facts rather than a single ambiguous notion of "same":

• corpus identity and authority head;
• current visible-node state;
• current revision state and revision-history coverage;
• graph, triple, tag, lifecycle, and sentinel state;
• extension/schema/machinery coverage;
• materialization-byte equality.

When custom SQL or semantic extensions are outside the comparator's declared coverage, report that incompleteness rather than implying full semantic equivalence.

Acceptance evidence

Tests distinguish identical visible content with different revision identity, triple-only and tag-only changes, extension-data changes, and custom executable-schema changes.

Related to #22.

[jacksenpierce]

Post-PM4 triage: still open, but scoped to explicit comparison coverage rather than workspace composition. The desired output should distinguish authority head, visible content, revision history, graph/triple/tag state, extensions, machinery, and byte equality without collapsing them into one same result.