feat(diagnostics): turn on warnings about width

[roife]

Summary

• 将 diagnostics.slang.warnings 的默认值改为开启 width-expand、width-trunc、port-width-expand、port-width-trunc
• 同步更新 VS Code 生成配置和 user-config schema，确保编辑器展示和运行时默认一致
• 增加回归测试，覆盖默认告警生效和显式空配置可关闭告警这两条路径

Testing

• cargo test -p vide
• cargo xtask check-config-artifacts
• cargo xtask check-schemas

[Copilot]

Pull request overview

This PR updates Vide’s default Slang diagnostics configuration to enable width-related warnings by default, and keeps the runtime defaults aligned with the published user-config schema and the VS Code extension’s generated configuration.

Changes:

• Enable width-expand, width-trunc, port-width-expand, and port-width-trunc by default in diagnostics.slang.warnings.
• Update the user-config JSON schema and VS Code extension defaults to match the new runtime defaults.
• Add regression tests covering (1) default warnings being emitted and (2) explicit empty warnings: [] suppressing the warning.

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/tests.rs	Adds regression tests verifying default port-width warnings are emitted and can be suppressed via explicit empty warnings.
src/config/user_config.rs	Introduces a default warning list constant and wires it into config defaults, schema defaults, and config metadata; adds parsing/default tests.
schemas/v1/user-config.schema.json	Updates schema defaults to reflect the new enabled-by-default width warning groups.
editors/vscode/src/generated/configuration.ts	Updates generated VS Code configuration defaults for diagnostics.slang.warnings.
editors/vscode/package.json	Updates the VS Code extension setting default array for vide.diagnostics.slang.warnings.

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Docs preview: https://vide.pascal-lab.net/preview/pr-214/