SMF-PR5: Add canonical platform metadata lint gate #261

Job	Run time
Lint & format	7s
Type check	42s
Validate v6 lead scoring dataset	40s
Validate v7 lead scoring dataset	38s
Tests (Python 3.11)	3m 18s
Release artifacts in sync (PR 7.2.1)	37s
Validate lead scoring dataset	35s
Tests (Python 3.12)	3m 35s
Execute release notebooks (G13.1)	1m 15s
	11m 27s

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