fix(ci): harden desktop prerelease tag computation #24079

Job	Run time
Test and Build / Build App	9m 0s
Test and Build / Lint and Test	3m 51s
Build AMD64	0s
Detect Version	0s
Build ARM64 (GHCR Only)	0s
Migrate Dev DB	0s
Check Docs Changes	0s
Deploy Trigger.dev (Dev)	0s
Check Desktop Signing Secrets	0s
Create Desktop Prerelease	0s
Build Dev ECR	0s
Desktop Prerelease Build	0s
Publish Desktop Prerelease	0s
Prune Desktop Prereleases	0s
Detect Desktop Changes	-9s
Promote Images	0s
Migrate DB	0s
Create GHCR Manifests	0s
Process Docs	0s
Create GitHub Release	0s
Desktop Release	0s
	12m 42s

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