feat(review): review_version 1.2 with answers, pre-existing, rounds and policy fields

MIGRATION.md

@@ -10,3 +10,28 @@ path — see [`GOVERNANCE.md`](https://git.fromaitochitta.com/open/ktg-plugin-ma
 
 Prior version migration notes (v1→v2, v2→v3) are preserved in
 `CHANGELOG.md` only.
+
+## review_version 1.2 (from the next release)
+
+`review.md` moves from `review_version: "1.1"` to `"1.2"`. Everything new is
+optional, and each field or section is checked for its shape only when it is
+present:
+
+- frontmatter `round`, `round_base`, `review_policy`, `review_policy_note`,
+  `review_policy_sha256` and `finalized`;
+- in the trailing JSON block, per finding `pre_existing`, `carried_from` and
+  `instruction_ref`, and at the top level `pre_existing_counts`, `resolved`
+  and `ran`;
+- the sections `## Answers` (the operator's answer to each counting MAJOR),
+  `## Pre-existing` and `## Resolved since round <n>`;
+- three `## Declined to Judge` reasons: `policy:skip`, `policy:cap` and
+  `instruction-out-of-set`.
+
+N-1 window: a 1.1 review validates unchanged for one minor version, and only
+with a warning after that. No reader fails on a 1.1 review: the validator,
+`/trekplan` and the verdict gate all read it.
+
+Gate change: a WARN opens the merge only when the verdict gate finds every
+counting MAJOR answered. That holds for a 1.1 review too, so a 1.1 WARN with a
+MAJOR keeps the merge lock closed until the MAJOR is answered; a 1.1 WARN
+without a MAJOR is read as before.