fix(alias): reject malformed RC_HOST credentials

[overtrue]

Related Issue(s)

None.

Problem Background and User Impact

Recent RC_HOST_* environment alias support lets users configure aliases without writing credentials to disk. The happy path was covered, but malformed environment alias values could still regress without a user-facing test. In particular, invalid percent escapes inside credentials were accepted as literal secret text, and some validation messages were classified as generic JSON errors instead of usage errors.

Root Cause Summary

The credential decoder delegated directly to urlencoding::decode, which tolerates malformed percent triplets such as %ZZ. The JSON error metadata inference also did not treat messages using “must use” or “must include” as usage errors.

Solution Overview

This PR adds strict percent-triplet validation before decoding RC_HOST credentials and keeps invalid credential values out of errors. It also broadens JSON error metadata inference for validation messages that say a value must use or include something. The CLI integration tests now cover malformed RC_HOST percent encoding and unsupported schemes while asserting credentials are not echoed.

Test Status

• cargo test -p rc-core test_parse_rc_host_alias_rejects_invalid_percent_encoding --lib
• cargo test -p rustfs-cli --test env_alias
• cargo fmt --all --check
• git diff --check
• make pre-commit

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[Copilot]

Pull request overview

This PR tightens validation and improves user-facing error classification for RC_HOST_* environment aliases, ensuring malformed percent-encoding is rejected and that JSON error output correctly categorizes common validation messages as usage errors.

Changes:

• Add strict percent-triplet validation for env alias credentials before decoding, rejecting malformed %.. sequences.
• Add unit + CLI integration tests to cover invalid percent-encoding and unsupported URL schemes, asserting credentials are not echoed.
• Broaden JSON error metadata inference to treat “must use” / “must include” validation messages as usage_error.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
crates/core/src/alias.rs	Adds strict percent-encoding validation for RC_HOST credentials and a unit test for malformed escapes.
crates/cli/tests/env_alias.rs	Adds integration tests ensuring malformed RC_HOST aliases fail without leaking credentials and are classified as usage errors.
crates/cli/src/output/formatter.rs	Expands heuristic classification so “must use/include” validation messages map to usage_error.

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