fix(test): Complete rootCtx initialization fix for all hanging tests (issue #355)

Problem:
- TestFallbackToDirectModeEnablesFlush hung with database deadlock
- TestIdempotentImportNoTimestampChurn and TestImportMultipleUnchangedIssues also hung
- All three tests call flushToJSONL() or autoImportIfNewer() which require rootCtx

Solution:
Applied the same rootCtx initialization pattern from v0.24.1 (commit 822baa0)
to the remaining hanging tests:
- TestFallbackToDirectModeEnablesFlush in direct_mode_test.go
- TestIdempotentImportNoTimestampChurn in import_idempotent_test.go
- TestImportMultipleUnchangedIssues in import_idempotent_test.go

Results:
- Before: Tests hung for 5+ minutes with database deadlock
- After: All tests pass in ~0.1s each

Fixes #355

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

cmd/bd/import_idempotent_test.go

@@ -218,6 +218,14 @@ func strPtr(s string) *string {
 // TestIdempotentImportNoTimestampChurn verifies that importing unchanged issues
 // does not update their timestamps (bd-84)
 func TestIdempotentImportNoTimestampChurn(t *testing.T) {
+	// FIX: Initialize rootCtx for autoImportIfNewer (issue #355)
+	testRootCtx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	oldRootCtx := rootCtx
+	rootCtx = testRootCtx
+	defer func() { rootCtx = oldRootCtx }()
+
 	// Create temp directory
 	tmpDir, err := os.MkdirTemp("", "bd-test-idempotent-*")
 	if err != nil {
@@ -300,6 +308,14 @@ func TestIdempotentImportNoTimestampChurn(t *testing.T) {
 // TestImportMultipleUnchangedIssues verifies that importing multiple unchanged issues
 // does not update any of their timestamps (bd-84)
 func TestImportMultipleUnchangedIssues(t *testing.T) {
+	// FIX: Initialize rootCtx for autoImportIfNewer (issue #355)
+	testRootCtx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
+	defer cancel()
+
+	oldRootCtx := rootCtx
+	rootCtx = testRootCtx
+	defer func() { rootCtx = oldRootCtx }()
+
 	// Create temp directory
 	tmpDir, err := os.MkdirTemp("", "bd-test-changed-*")
 	if err != nil {