fix(driver-sql,cli): a unique index its rows violate is declared not appliable, per entry

Co-authored-by: Claude <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YRXQdFH1TrCyDQ5L1xDQRg

Author: claude

packages/cli/src/utils/schema-migrate.ts

@@ -1564,8 +1564,9 @@ export async function bootSchemaStack(
           + 'has a database whose apply limit can be read.',
         );
       }
-      // A driver that declares nothing applies what the differ means it to.
-      return owner.driftApplyLimit ? owner.driftApplyLimit(entry.op.type) : null;
+      // The entry's own limit first (a unique index its rows violate, ADR-0120
+      // D4), then the driver's for its op type; neither, and it applies.
+      return entry.applyLimit ?? (owner.driftApplyLimit ? owner.driftApplyLimit(entry.op.type) : null);
     },
     managedTableCount,
     kernel,

packages/drivers/driver-sql/src/schema-drift.ts

@@ -404,6 +404,18 @@ export interface ManagedDriftEntry extends SchemaDiffEntry {
   op: DriftOp;
   /** Human one-liner with an actionable hint. */
   message: string;
+  /**
+   * [ADR-0120 D4] Why the reporting driver's apply door will not perform THIS
+   * entry on this database, read from its data when the entry was reported —
+   * absent when nothing in the data stops it. The duplicate pre-flight sets it
+   * on a unique index the existing rows already violate (the conflicting
+   * groups are the reason): the apply refuses it however it is confirmed, so
+   * `os migrate plan` / `apply` list the entry with this reason and never offer
+   * `--allow-destructive` for it. The one structured form of that judgement;
+   * ⛔ never re-derived from {@link message}. A limit of a whole op type on a
+   * transport is the driver's own `driftApplyLimit`, not this.
+   */
+  applyLimit?: string;
 }
 
 /**

packages/drivers/driver-sql/src/sql-driver.ts

@@ -14190,6 +14190,10 @@ export class SqlDriver implements IDataDriver {
       const report = formatDuplicateGroups(duplicates);
       d.category = 'destructive';
       d.severity = 'error';
+      // The block, declared on the entry: `os migrate plan` / `apply` read it
+      // here and never offer `--allow-destructive` for an op the apply refuses
+      // on this data however it is confirmed.
+      d.applyLimit = `existing rows already violate the unique key: ${report}`;
       d.message = nullSafeKey
         ? `${op.table}: cannot ${tighten ? 'tighten' : 'create'} '${op.indexName}' as ${signature} — existing rows ` +
           `already violate the NULL-safe unique constraint (duplicates the old index wrongly admitted: SQL ` +