feat(config): DOT_BULLETIN_RPC override + chaos-rpc cell (Phase 6 S18)

[EnderOfWorlds007]

Phase 6 S18 — RPC failover chaos test.

Summary

• New DOT_BULLETIN_RPC env var overrides the primary Bulletin RPC in getChainConfig(), keeping the built-in URL as bulletinRpcFallbacks[0].
• bulletin-deploy's deploy() already builds [userRpc, DEFAULT] at runtime (verified in bundled JS), so storage.ts gets failover for free.
• playground.ts's dedicated metadata-upload client now uses [cfg.bulletinRpc, ...cfg.bulletinRpcFallbacks] to get the same failover.
• New nightly-chaos-rpc cell in test-nightly-publish sets DOT_BULLETIN_RPC=ws://127.0.0.1:1/ and asserts the deploy still completes via fallback.
• chaosDeployArgs() helper factors out duplicated CLI args from the SIGINT test.

Stacked on

• PR ci(e2e): Phase 7 — release-prerelease published-binary smoke #93 (Phase 7 published-binary). Once ci(e2e): Phase 7 — release-prerelease published-binary smoke #93 merges, will rebase onto main.

Key finding

DeployOptions.rpc is typed as string only, but bulletin-deploy's runtime builds a [userRpc, DEFAULT] endpoint list internally (chunk-A2J6R5PD.js line 679) and passes it to getWsProvider(BULLETIN_ENDPOINTS, ...). The .d.ts underdescribes the actual failover behavior.

[github-actions]

Dev build ready — try this branch:

curl -fsSL https://raw.githubusercontent.com/paritytech/playground-cli/main/install.sh | VERSION=dev/ci/e2e-phase-6-rpc-failover bash

[github-actions]

E2E Test Pass · ✅ PASS

Tag: e2e-ci-pr · Branch: ci/e2e-phase-6-rpc-failover · Commit: 9e20f8a · Run logs

Cell	Result	Time
pr-deploy-foundry	✅ PASS	1m48s
pr-deploy-frontend	✅ PASS	9m48s
pr-init-session	✅ PASS	1m14s
pr-mod	✅ PASS	2m09s
pr-preflight	✅ PASS	2m06s
pr-install	✅ PASS	0m41s
${{ matrix.cell }}	⏭️ SKIP	0m00s
${{ matrix.cell }}	⏭️ SKIP	0m00s

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