Add independent log parser fixtures

[mohamedjaazeer4-sketch]

Summary

Adds independent hand-written log parser fixtures for tools/log_aggregator.py and a focused validation test covering:

• structured JSON log parsing
• plain text log parsing
• nginx access log parsing
• malformed JSON handling
• aggregator parser routing for nginx logs

Also updates parser order from:

[JSONLogParser(), TextLogParser(), NginxLogParser()]

to:

[JSONLogParser(), NginxLogParser(), TextLogParser()]

This prevents the generic text parser from swallowing nginx access logs before NginxLogParser can parse them.

Validation performed

python3 tests/test_log_aggregator_independent_fixtures.py
python3 -m py_compile tools/log_aggregator.py tests/test_log_aggregator_independent_fixtures.py

Focused test result:

PASS test_json_fixture
PASS test_plain_text_fixture
PASS test_nginx_fixture_direct_parser
PASS test_malformed_json_does_not_crash_json_parser
PASS test_aggregator_routes_nginx_before_generic_text_parser
ALL LOG AGGREGATOR FIXTURE TESTS PASSED

Full build note

I attempted the full build locally, but the environment is missing npm, so the frontend build could not run.

Error:

FileNotFoundError: [Errno 2] No such file or directory: 'npm'

Notes

The fixtures are hand-written representative examples and are not generated by the parser implementation.