fix(results): reject uppercase primary bundles

[joeharris76]

Summary

• require primary result bundles to use the lowercase .json extension recognized by the submission-validation workflow
• preserve case-insensitive rejection of companion bundles and manifest files
• cover validation, corpus inventory generation, and Results Explorer ingestion against uppercase-primary bypasses

Context

Follow-up to the unresolved P1 review finding on #1444: an uppercase primary such as result.JSON could bypass the workflow's lowercase *.json validation pathspec while still being ingested downstream.

Verification

• uv run -- python -m pytest -n 0 tests/unit/scripts/test_validate_submission.py tests/unit/scripts/test_generate_corpus_inventory.py tests/unit/scripts/explorer_pipeline/test_pipeline.py -k "uppercase_primaries" -q
• uv run -- python -m pytest -n 0 tests -k "bundle or submission or inventory" -q
• cd results-explorer && npm run typecheck && npm test
• uv run -- python -m pytest -n 0 -m fast -q
• PYTEST_ADDOPTS='-n 0' make pr-preflight

Closes the post-merge review follow-up tracked by pr1444-uppercase-primary-validation-bypass-20260801-2.

[joeharris76]

Closing as superseded by merged #1449. That PR implemented the reviewer-approved case-insensitive workflow fix and resolved the original #1444 P1 thread; this branch would unnecessarily narrow the accepted bundle contract after that repair.

[chatgpt-codex-connector]

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