chore(js-ts): Type signatureRequest reducer and remove any from RootState

[devin-ai-integration]

Summary

Part of Workstream 4 (type Redux reducers, eliminate any from RootState). The signatureRequest reducer and action were already TypeScript, so this only exports the state interface and wires it into RootState:

// app/reducers/signatureRequest/index.ts
export interface SignatureRequestState { securityAlertResponse?: SecurityAlertResponse; }

// app/reducers/index.ts
- signatureRequest: any;   // + eslint-disable
+ signatureRequest: SignatureRequestState;

Cascade (errors previously hidden by any)

The reducer state stores the BlockaidBanner SecurityAlertResponse (enum reason/result_type, features: (string | Record)[]), which is not assignable to the transaction-controller SecurityAlertResponse (features: string[]) that selectSignatureSecurityAlertResponse declares and its consumers rely on (it's ??-merged with transactionMetadata.securityAlertResponse). These two types genuinely diverge, so the selector now casts at that boundary to preserve its existing public contract:

): { securityAlertResponse: SecurityAlertResponse /* tx-controller */ } =>
  rootState.signatureRequest as unknown as { securityAlertResponse: SecurityAlertResponse };

Test fixtures that put a securityAlertResponse into the now-typed signatureRequest slot are reconciled by typing the shared securityAlertResponse helper in confirm-data-helpers.ts as the BlockaidBanner shape (fixes security-alerts, confirm-component, useSignatureMetrics, useSecurityAlertResponse, signature-blockaid-banner tests transitively). TypedSign/index.test.tsx's inline fixture and initial-root-state.ts (signatureRequest: {}) are adjusted directly.

Behavior is unchanged — types only.

Validation

• yarn tsc — 0 errors
• yarn lint — 0 errors (warnings only)
• yarn jest on the affected selector/hook/component tests — 33 tests pass

Link to Devin session: https://app.devin.ai/sessions/150060d9c6a14a1b9ee04e5a407b3f8b
Requested by: @WesternConcrete

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