Add an expected-guided simplification step to state error derivations

[CatarinaGamboa]

Problem

The final Found step in a state error can contain facts from state sets unrelated to Expected. The user must identify the relevant fact and trace version equalities manually.

Current example

The last simplification step for preview.setTiling(...) is:

Expected concerns the tiling state of preview³⁰⁴. The relevant startTiling(preview²⁹⁹) fact and the version link are present, but compression facts remain in the final explanation.

Desired behavior

Append a step labeled “Relevant to this requirement” after the existing simplification steps when the verifier can safely produce one. In this example, it should retain startTiling(preview²⁹⁹) and the equality needed to relate its tiling state to preview³⁰⁴. It should omit compression facts only if their independence from this requirement has been established. The back arrow should return to the full step shown above.

This is a simplification step in the error display. It must not change the verification condition checked by the solver or the verification result.

Implementation direction

1. Give the new pass both Expected and the simplified Found expression. VCChecker.throwStateRefinementError has both when it constructs the error.
2. Use expression and state set information to identify the receiver, relevant state set, and necessary version equalities.
3. Remove a clause only when its independence has been established. Keep clauses whose role is uncertain.
4. Append the result to the derivation history with the metadata needed for source links and backward navigation. Do not infer dependencies from rendered names.

Acceptance criteria

• The scanner error gains a final “Relevant to this requirement” step showing the startTiling fact and every necessary version link.
• Proven independent compression facts are omitted; uncertain facts remain.
• The existing full step remains available through the back arrow.
• No step is added when safe cleanup cannot be established.
• Verification results do not change.