fix showcase daily navigation and rebuild hub index

[adamvangrover]

This commit resolves frontend navigation and linking issues within the showcase directory by rebuilding the Adam Daily Hub Index to correctly link to all newly generated files and updating the data/adam_daily/index.html navigation array mapping to ensure dates link to proper markdown/html briefs instead of raw JSON files.

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PR created automatically by Jules for task 12942602395102281489 started by @adamvangrover

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