fix: security and correctness follow-ups for Sepolia operator tooling (PR #176)

[piotr-roslaniec]

Context

Follow-up to #176 (Sepolia TokenStaking deploy, ExtendedTokenStaking upgrade, and operator setup tooling). Addresses security and correctness issues identified in code review.

Changes

P0 -- Private key exposure

• scripts/create-operator-keystore.js -- remove console.log("Private key:", ...). Address and keystore path are sufficient output.
• scripts/get-operator-key.js -- same; remove private key log line.
• scripts/setup-new-staking-provider.js -- remove NEW_STAKING_PROVIDER_KEY and NEW_OPERATOR_KEY from generated .env files (keys written to disk are a git add . leak risk). Staking provider key is still printed once to terminal with a "copy now" warning since it is generated ephemerally.

P1 -- Keys in CLI arguments

• scripts/run-new-operator-setup.sh -- replace all --private-key $KEY flags with ETH_PRIVATE_KEY="$KEY" cast send via _sp_cast_send_ok / _op_cast_send_ok wrappers. --private-key exposes the raw key in ps aux and shell history.
• scripts/fund-new-operator.sh -- same for the deployer key.

P1 -- Operator key script bugs

• scripts/get-operator-key.js -- remove hardcoded UUID default path (c88df450-...) that caused ENOENT for all users except the original developer. Require explicit path argument with usage error.
• scripts/get-operator-key.js -- fix --list directory path: ../../operator-1-keystore resolved above the repo root; corrected to ../operator-1-keystore.

P1 -- Proxy upgrade kind

• deploy/54_upgrade_token_staking_extended.ts -- remove hardcoded kind: "transparent" from upgradeProxy options. Let the OZ plugin infer the proxy type. Hardcoding risks a mismatch if the plugin defaulted differently during the original deploy. Add a comment with the cast storage command to verify the proxy type on-chain before any future mainnet run.

P2 -- Code quality and correctness

• scripts/create-operator-keystore.js and scripts/setup-new-staking-provider.js -- require non-empty password; empty-password keystores are trivially decryptable.
• deploy/54_upgrade_token_staking_extended.ts -- replace two inline const fs = require("fs") with a single top-level import * as fs from "fs".
• deployments/mainnet/TokenStaking.json -- restore file deleted without explanation in Sepolia TokenStaking proxy deploy, ExtendedTokenStaking upgrade, and operator setup tooling #176. Downstream consumers relying on deployments/mainnet/ break silently.
• contracts/staking/TokenStaking.sol -- add application != address(0) guard in increaseAuthorization for consistency with approveApplication.

Housekeeping (async refactor in scripts)

The three JS scripts were also converted from sync fs.*Sync calls to fs.promises.* and gained try/catch inside main(). This was required to pass the pre-commit UBS scan (sync I/O in scripts triggers a warning) but also makes error handling explicit.

Test plan

• node scripts/create-operator-keystore.js without args exits with usage error
• node scripts/create-operator-keystore.js mypassword creates keystore, prints address only (no key)
• node scripts/get-operator-key.js without args exits with usage error
• node scripts/get-operator-key.js --list lists keystores from operator-1-keystore/ (not parent dir)
• node scripts/setup-new-staking-provider.js without args exits with usage error
• node scripts/setup-new-staking-provider.js mypassword generates wallets; .env.new-operator contains addresses but no private keys; terminal shows SP key with warning
• deployments/mainnet/TokenStaking.json exists and has correct address 0x01B67b1194C75264d06F808A921228a95C765dd7
• yarn compile passes