fix(autoimport): prevent export to wrong JSONL file (bd-tqo)

Add FindJSONLInDir helper that correctly prefers issues.jsonl over other
.jsonl files. Previously, glob patterns could return deletions.jsonl or
merge artifacts (beads.base.jsonl, etc.) first alphabetically, causing
issue data to be written to the wrong file.

This fixes the root cause of deletions.jsonl corruption where full issue
objects were written instead of deletion records, leading to all issues
being purged during sync.

Changes:
- Add FindJSONLInDir() in internal/autoimport with proper file selection
- Update AutoImportIfNewer() to use FindJSONLInDir
- Update CheckStaleness() to use FindJSONLInDir
- Update triggerExport() in RPC server to use FindJSONLInDir
- Add comprehensive tests for FindJSONLInDir

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

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

internal/rpc/server_export_import_auto.go

@@ -441,15 +441,9 @@ func hasUncommittedBeadsFiles(workspacePath string) bool {
 // CRITICAL: Must populate all issue data (deps, labels, comments) to prevent data loss
 func (s *Server) triggerExport(ctx context.Context, store storage.Storage, dbPath string) error {
 	// Find JSONL path using database directory
+	// Use FindJSONLInDir to prefer issues.jsonl over other .jsonl files (bd-tqo fix)
 	dbDir := filepath.Dir(dbPath)
-	pattern := filepath.Join(dbDir, "*.jsonl")
-	matches, err := filepath.Glob(pattern)
-	var jsonlPath string
-	if err == nil && len(matches) > 0 {
-		jsonlPath = matches[0]
-	} else {
-		jsonlPath = filepath.Join(dbDir, "issues.jsonl")
-	}
+	jsonlPath := autoimport.FindJSONLInDir(dbDir)
 
 	// Get all issues from storage
 	sqliteStore, ok := store.(*sqlite.SQLiteStorage)