Implement change-set comparison and deterministic impact analysis

Plan ID

EM-05

Purpose

Complete the change-set analysis needed for reviewable specification changes and downstream materialization.

Scope

• Implement change-set list, show, update, and compare operations.
• Report stable-ID changes, exact duplicates, declared conflicts, supersession, and dependency cycles.
• Implement deterministic impact candidate generation from interface/scope intersections and explicit relationships.
• Record applicable/not-applicable dispositions, rationale, and mechanical/semantic origin.
• Enforce approved change-set immutability and base-commit rules.
• Produce structured output suitable for pull-request summaries.

Dependencies

Depends on EM-04. The caller-facing result contract is defined by #30.

Acceptance criteria

• Repeated analysis of the same fixture produces byte-identical output.
• Candidate generation prefers false positives to missed explicit obligations.
• Missing dispositions prevent approval when candidates exist.
• Approved manifests cannot be modified.
• Golden fixtures cover additions, revisions, retirements, conflicts, supersession, cycles, and scope intersections.

Out of scope

Semantic requirement review remains with the agent and human. WMS materialization belongs to later issues.

Read EM-04 and issue #30 first to establish the dependency and caller-facing result contract, then locate the existing change-set and impact-analysis entry points in the Go repository. Use golden fixtures covering additions, revisions, retirements, conflicts, supersession, cycles, and scope intersections; done means repeated analysis is byte-identical and all listed acceptance criteria hold.