Fix all gosec, misspell, and unparam linter errors

- Add #nosec directives with explanations for all gosec warnings in worktree operations
- Tighten directory permissions from 0755 to 0750 for better security
- Fix misspellings: archaeological -> archeological, cancelled -> canceled
- Remove unused jsonlPath parameter from syncBranchCommitAndPush
- Change branchExists to return bool instead of (bool, error) - error was never used

All changes maintain backward compatibility and improve code quality.

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

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

internal/rpc/server_export_import_auto.go

@@ -260,7 +260,7 @@ func (s *Server) checkAndAutoImportIfStale(req *Request) error {
 			// But capture store reference before goroutine to ensure it's not closed
 			go func(s *Server, store storage.Storage, dbPath string) {
 				// Create independent context with timeout
-				// Don't derive from importCtx as that may be cancelled already
+				// Don't derive from importCtx as that may be canceled already
 				exportCtx, exportCancel := context.WithTimeout(context.Background(), 10*time.Second)
 				defer exportCancel()