FN-5700: remove duplicate task autoMerge declarations

Clean up duplicate task autoMerge declarations across core schema, store mapping, and tests.

- Remove the redundant task-level autoMerge field from core Task types and DB schema expectations.
- Keep task hydration autoMerge mapping in a single path and normalize boolean conversion to explicit integer checks.
- Update affected core and roadmap store tests to match the deduplicated autoMerge surface.

Files changed:
 packages/core/src/__tests__/db-migrate.test.ts     | 12 ++++----
 packages/core/src/__tests__/db.test.ts             | 34 +++++++++++-----------
 packages/core/src/__tests__/goals-schema.test.ts   |  2 +-
 packages/core/src/__tests__/insight-store.test.ts  | 10 +++----
 packages/core/src/__tests__/mission-store.test.ts  |  2 +-
 packages/core/src/__tests__/run-audit.test.ts      |  2 +-
 packages/core/src/__tests__/secrets-schema.test.ts |  6 ++--
 .../core/src/__tests__/store-merge-queue.test.ts   |  2 +-
 packages/core/src/__tests__/task-documents.test.ts |  2 +-
 packages/core/src/db.ts                            |  1 -
 packages/core/src/store.ts                         |  4 +--
 packages/core/src/types.ts                         |  5 ----
 .../src/store/__tests__/roadmap-store.test.ts      |  4 +--
 13 files changed, 39 insertions(+), 47 deletions(-)

Fusion-Task-Id: FN-5700

Fusion-Task-Lineage: d2d4d41e-31b1-44a0-9594-9d75056c59a2

plugins/fusion-plugin-roadmap/src/store/__tests__/roadmap-store.test.ts

@@ -743,8 +743,8 @@ describe("RoadmapStore", () => {
   });
 
   describe("schema version", () => {
-    it("schema version is 95 after init", () => {
-      expect(db.getSchemaVersion()).toBe(95);
+    it("schema version is 96 after init", () => {
+      expect(db.getSchemaVersion()).toBe(96);
     });
   });