Add an informative error message when "--download-resources" has not yet been run

[evolarjun]

Right now it just returns a stack trace e.g.:

$ amrrules --input tests/data/input/test_ecoli_wildtype.tsv --output-prefix test_ecoli_wildtype --organism 's__Escherichia coli'

Traceback (most recent call last):
  File "/netmnt/vast01/gp/home/aprasad/micromamba/envs/amrrules_beta/bin/amrrules", line 7, in <module>
    sys.exit(main())
             ^^^^^^
  File "/netmnt/vast01/gp/home/aprasad/src/AMRrules/src/amrrules/cli.py", line 62, in main
    rules_engine.run(args)
  File "/netmnt/vast01/gp/home/aprasad/src/AMRrules/src/amrrules/rules_engine.py", line 32, in run
    card_drug_map = rm().get_card_drug_class_map() # get CARD drugs and their associated classes
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/netmnt/vast01/gp/home/aprasad/src/AMRrules/src/amrrules/resources.py", line 312, in get_card_drug_class_map
    self._card_drug_map = self._extract_card_drugs(str(obo_file), str(categories_file))
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/netmnt/vast01/gp/home/aprasad/src/AMRrules/src/amrrules/resources.py", line 259, in _extract_card_drugs
    card_ontology = obonet.read_obo(obo_file_path)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/netmnt/vast01/gp/home/aprasad/micromamba/envs/amrrules_beta/lib/python3.12/site-packages/obonet/read.py", line 37, in read_obo
    with open_read_file(path_or_file, encoding=encoding) as obo_file:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/netmnt/vast01/gp/home/aprasad/micromamba/envs/amrrules_beta/lib/python3.12/site-packages/obonet/io.py", line 49, in open_read_file
    return opener(path, "rt", encoding=encoding)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/netmnt/vast01/gp/home/aprasad/src/AMRrules/src/amrrules/resources/aro.obo'

$ amrrules --download-resources
Downloading ReferenceGeneHierarchy.txt from https://ftp.ncbi.nlm.nih.gov/pathogen/Antimicrobial_resistance/AMRFinderPlus/database/latest/ReferenceGeneHierarchy.txt...
Successfully downloaded ReferenceGeneHierarchy.txt
Downloading version.txt from https://ftp.ncbi.nlm.nih.gov/pathogen/Antimicrobial_resistance/AMRFinderPlus/database/latest/version.txt...
Successfully downloaded version.txt
AMRFinderPlus database version: 2026-01-21.1
AMRFinderPlus database files downloaded successfully.
Downloading https://card.mcmaster.ca/download/5/ontology-v4.0.1.tar.bz2...
Extracting ./aro.obo as aro.obo...
Extracting ./ncbi_taxonomy.tsv as ncbi_taxonomy.tsv...
Downloading https://card.mcmaster.ca/download/0/broadstreet-v4.0.1.tar.bz2...
Extracting ./aro_categories.tsv as aro_categories.tsv...
CARD archives downloaded and extracted successfully.
All required files are present in the resources directory.
All resources have been successfully set up.
Resource download complete.
$ amrrules --input tests/data/input/test_ecoli_wildtype.tsv --output-prefix test_ecoli_wildtype --organism 's__Escherichia coli'
3 hits matched a rule and 2 hits did not match a rule.
Output written to /netmnt/vast01/gp/home/aprasad/src/AMRrules/test_ecoli_wildtype_interpreted.tsv.
Summary output written to /netmnt/vast01/gp/home/aprasad/src/AMRrules/test_ecoli_wildtype_genome_summary.tsv.