fix(deploy): remove unreachable null-signer guard in resolveSignerSetup

[EnderOfWorlds007]

Context

Closes #104 (Bug 2).

Bug 1 from that issue (error message not mentioning --suri) was already fixed on main — SignerNotAvailableError now reads 'No signer available. Run "dot init" to log in, or pass --suri //Alice for dev.'

This PR addresses Bug 2 only.

Problem

resolveSignerSetup in src/utils/deploy/signerMode.ts contained a dead error branch:

if (opts.publishToPlayground) {
    if (!opts.userSigner) {
        throw new Error(
            'Publishing to Playground requires a logged-in account. Run "dot init" first, or drop --playground.',
        );
    }
    ...
}

The !opts.userSigner guard can never be true when publishToPlayground is true. The invariant is enforced one level up:

• shouldResolveUserSigner() returns true whenever opts.publishToPlayground === true (signerMode.ts:256)
• When that returns true, resolveSigner() is called in the preflight (deploy/index.ts:203)
• resolveSigner() either produces a ResolvedSigner or throws SignerNotAvailableError — it never returns null
• The preflight rethrows any SignerNotAvailableError when publishToPlayground is set (deploy/index.ts:208-209)

So by the time resolveSignerSetup is called, userSigner is guaranteed non-null. The throw was dead code.

Fix

• Delete the if (!opts.userSigner) throw branch
• Replace with opts.userSigner! (non-null assertion) to keep TypeScript happy
• Add a comment explaining the invariant so a future refactor doesn't silently reintroduce the same guard thinking it's needed

Testing

• pnpm exec tsc --noEmit — passes clean
• No behaviour change on any reachable path

[github-actions]

Dev build ready — try this branch:

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

[github-actions]

E2E Test Pass · ✅ PASS

Tag: e2e-ci-pr · Branch: fix/dead-signer-guard · Commit: d1b2562 · Run logs

Cell	Result	Time
pr-deploy-foundry	✅ PASS	1m34s
pr-deploy-frontend	✅ PASS	8m45s
pr-mod	✅ PASS	1m25s
pr-install	✅ PASS	0m42s
pr-preflight	✅ PASS	3m28s
pr-init-session	✅ PASS	1m21s
${{ matrix.cell }}	⏭️ SKIP	0m00s
${{ matrix.cell }}	⏭️ SKIP	0m00s

Sentry traces: view spans for this run