feat(relation): refuse retrospective reporting as a transition

[seonghobae]

Retrospective reporting may point at earlier event time (ADR 0002/0003). It cannot become a forward state transition or a translation. Recovery is the computed share of recovered reporting kinds that match known truth versus collapsing every report to a contemporaneous forward report.

Complementary to #136 (translation_edge) and #120 (citation_edge). This crate owns retrospective-versus-transition/translation identity.

Local gates:

• cargo test -p retrospective_edge --all-targets GREEN after RED (package did not exist)
• clippy -D warnings PASS
• workspace contract PASS
• docstring contract PASS
• lines 17/17; nightly-2026-08-01 branches 6/6

Does not allocate migration 0008. Does not recreate translation_edge or citation_edge.

Keep this PR draft. Preferred merge remains #46 only when exact-head required Checks pass and a qualifying independent (non-Cursor/CodeRabbit) APPROVE exists. OpenCode CHANGES_REQUESTED on #46 is a coverage-evidence race (live checks are green) — do not empty-commit.

[coderabbitai]

Important

Review skipped

Draft detected.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: d0c25c76-0017-4482-b0ad-d09c12045516

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}