Fix direct VLESS and other share-link imports

[wnlen]

Summary

• accept direct vmess://, vless://, trojan://, tuic://, hysteria2://, hy2://, and anytls:// inputs in clash add
• classify direct share links as convert and pass them intact to the local subconverter
• redact credential-bearing share links from command feedback, subscription displays, cache metadata, and converter diagnostics
• skip the invalid Clash YAML download fallback when a direct share link converts to zero nodes
• document direct share-link usage

Verification

• bash scripts/dev/check-direct-share-link-add.sh
• bash scripts/dev/check-runtime-config-normalization.sh
• bash scripts/dev/check-subscription-download-failure.sh
• bash scripts/dev/check-sub-update-compat.sh
• bash scripts/dev/check-clash-command-entry.sh
• bash -n scripts/core/config.sh scripts/core/clashctl.sh scripts/dev/check-direct-share-link-add.sh
• git diff --check

Fixes #315