feat(FN-3220): add regression tests for branch routing and merge-target beh

Adds regression tests for branch-mode behavior across CLI, core, and dashboard: CLI PR base branch inheritance (task-lifecycle), mission triage branch routing and merge-target trimming (task-merge), and subtask branch-mode UI coverage (SubtaskBreakdownModal, mission-e2e).

Fusion-Task-Id: FN-3220

packages/core/src/__tests__/store.test.ts

@@ -11462,7 +11462,7 @@ describe("RunMutationContext", () => {
       await rm(localRoot, { recursive: true, force: true });
       await rm(localGlobal, { recursive: true, force: true });
     }
-  }, 20_000);
+  }, 60_000);
 
   it("addComment() with runContext includes runContext in log entry", async () => {
     const localRoot = makeTmpDir();

packages/core/src/__tests__/task-merge.test.ts

@@ -44,6 +44,21 @@ describe("resolveTaskMergeTarget", () => {
     });
   });
 
+  it("trims inherited branch context before using it", () => {
+    expect(resolveTaskMergeTarget({
+      baseBranch: undefined,
+      branchContext: {
+        groupId: "G-1",
+        source: "planning",
+        assignmentMode: "shared",
+        inheritedBaseBranch: "  release/2026.10  ",
+      },
+    })).toEqual({
+      branch: "release/2026.10",
+      source: "task-branch-context",
+    });
+  });
+
   it("uses project default branch when task has no explicit target", () => {
     expect(resolveTaskMergeTarget(
       { baseBranch: undefined, branchContext: undefined },