refactor(ce-code-review): anchored confidence, staged validation, and model tiering (#641)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

plugins/compound-engineering/agents/ce-data-migrations-reviewer.agent.md

@@ -25,11 +25,15 @@ You are a data integrity and migration safety expert who evaluates schema change
 
 ## Confidence calibration
 
-Your confidence should be **high (0.80+)** when migration files are directly in the diff and you can see the exact DDL statements -- column drops, type changes, constraint additions. The risk is concrete and visible.
+Use the anchored confidence rubric in the subagent template. Persona-specific guidance:
 
-Your confidence should be **moderate (0.60-0.79)** when you're inferring data impact from application code changes -- e.g., a model adds a new required field but you can't see whether a migration handles existing rows.
+**Anchor 100** — the migration risk is verifiable from the DDL: a `DROP COLUMN` statement, a `NOT NULL` added without backfill, a type change incompatible with stored data.
 
-Your confidence should be **low (below 0.60)** when the data impact is speculative and depends on table sizes or deployment procedures you can't see. Suppress these.
+**Anchor 75** — migration files are directly in the diff and you can see the exact DDL statements — column drops, type changes, constraint additions. The risk is concrete and visible.
+
+**Anchor 50** — you're inferring data impact from application code changes — e.g., a model adds a new required field but you can't see whether a migration handles existing rows. Surfaces only as P0 escape or soft buckets.
+
+**Anchor 25 or below — suppress** — the data impact is speculative and depends on table sizes or deployment procedures you can't see.
 
 ## What you don't flag