fix installer latest release resolution

[charlesHetterich]

Summary

• resolve installer latest versions from GitHub's no-body releases/latest redirect before checking jsDelivr
• keep jsDelivr as a fallback only, since it can lag freshly published releases
• preserve the existing VERSION override behavior

Verification

• bash -n install.sh
• zsh -n install.sh
• verified the patched resolution logic returns v0.18.1 locally

[github-actions]

Dev build ready — try this branch:

curl -fsSL https://raw.githubusercontent.com/paritytech/playground-cli/main/install.sh | VERSION=dev/fix/install-latest-release bash

[github-actions]

E2E Test Pass · ✅ PASS

Tag: e2e-ci-pr · Branch: fix/install-latest-release · Commit: 7687f41 · Run logs

Cell	Result	Time
pr-install	✅ PASS	1m02s
pr-preflight	✅ PASS	2m44s
pr-deploy-cdm	✅ PASS	3m53s
pr-mod	✅ PASS	1m27s
pr-init-session	✅ PASS	1m46s
pr-deploy-foundry	✅ PASS	1m31s
pr-deploy-frontend	✅ PASS	10m33s
${{ matrix.cell }}	⏭️ SKIP	0m00s
${{ matrix.cell }}	⏭️ SKIP	0m00s

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