fix: normalize error message prefix to ERROR: for consistency [fj4WqyCCw3C5ShR1RfB7MoBPTpkRrBFYP1uT35g3MvT]

[waterWang]

Summary

Fixes inconsistent error message formatting in tools/rustchain_wallet_cli.py per RustChain bounty #16253 / issue #7889.

Changes

Normalized error message prefix — all error messages now use ERROR: (uppercase) consistently instead of a mix of Error: and ERROR::

File	Line	Before	After
tools/rustchain_wallet_cli.py	213	Error: missing dependency	ERROR: missing dependency
tools/rustchain_wallet_cli.py	220	Error: password mismatch	ERROR: password mismatch
tools/rustchain_wallet_cli.py	249	Error: missing dependency	ERROR: missing dependency
tools/rustchain_wallet_cli.py	257	Error: password mismatch	ERROR: password mismatch
tools/rustchain_wallet_cli.py	295	Error: Server returned HTTP	ERROR: Server returned HTTP
tools/rustchain_wallet_cli.py	307	Error: Server returned JSON but not an object	ERROR: Server returned JSON but not an object
tools/rustchain_wallet_cli.py	481	Error: {e}	ERROR: {e}

Exit code scheme (unchanged, already documented in --help)

Exit codes:
  0  success
  1  usage / input error
  2  network / connectivity error
  3  bad / unexpected response from server
  4  wallet not found
  5  authentication / decryption failure
  6  unexpected internal error

Verification

The cmd_balance function already handles all expected failure paths correctly:

• Network error → EXIT_NETWORK_ERROR (2) with ERROR: on stderr ✅
• HTTP 404 → EXIT_WALLET_NOT_FOUND (4) with ERROR: on stderr ✅
• HTTP non-200 → EXIT_BAD_RESPONSE (3) with ERROR: on stderr ✅
• Non-JSON response → EXIT_BAD_RESPONSE (3) with ERROR: on stderr ✅
• Missing field in response → EXIT_BAD_RESPONSE (3) with ERROR: on stderr ✅
• Success → EXIT_SUCCESS (0) with JSON on stdout ✅
• Unknown exception → EXIT_UNKNOWN_ERROR (6) with ERROR: on stderr ✅

Closes: #7889

[github-actions]

Welcome to RustChain! Thanks for your first pull request.

Before we review, please make sure:

• Non-doc PRs have a BCOS-L1 or BCOS-L2 label
• Doc-only PRs are exempt from BCOS tier labels when they only touch docs/**, *.md, or common image/PDF files
• New code files include an SPDX license header
• You've tested your changes against the live node

Bounty tiers: Micro (1-10 RTC) | Standard (20-50) | Major (75-100) | Critical (100-150)

A maintainer will review your PR soon. Thanks for contributing!