feat(scripts): add PR pre-merge review helper script #9

Job	Run time
Verify Upstream Checksums	13s
ShellCheck	1m 27s
Pinned Ref Smoke (checksums from integration branch)	2m 26s
E2E curl\|bash Bootstrap	23s
E2E Resume After Failure	15m 15s
Workflow YAML Lint	7s
Test installer (Ubuntu 24.04, mode vibe)	16m 2s
Test installer (Ubuntu 25.10, mode vibe)	2m 33s
Test installer (Ubuntu 24.04, mode safe)	14m 52s
Manifest Drift Check	23s
Selection & Contract Tests	6s
	53m 47s

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