fix(umodel): surface authoring warnings during validation

[Chloride233]

Summary

Service.Validate now surfaces warning-only authoring hints for UModel elements that are schema-valid but may be less useful for downstream writes, filters, query display, or topology traversal.

The hints are intentionally narrow:

• entity_set without spec.fields gets a schema-guidance warning.
• metric_set metrics without both unit and data_format get a display-formatting warning.
• entity_set_link types prefixed with candidate_ or maybe_ get a provisional-link warning.

These warnings reuse the existing ValidationResult.Warnings field and do not reject model elements.

What stays unchanged

• Valid model elements remain valid.
• No REST, CLI, MCP schema, SDK, model schema, import, or graphstore behavior changes.
• Existing schema validation errors still come from the schema validator.
• Normal relation types such as related_to are not warned.
• Metrics with data_format but no unit are not warned.

Verification details

• Affected version: main; no released tag was used for this reproduction.
• Steps to reproduce before this change: Call Service.Validate with a schema-valid entity_set that has no spec.fields, a metric_set metric that has neither unit nor data_format, or an entity_set_link whose type starts with candidate_ or maybe_.
• Expected behavior: Validation remains successful and ValidationResult.Warnings identifies the relevant authoring field and explains why the missing or provisional metadata may reduce downstream usefulness.
• Actual behavior before this change: Validation succeeds, but no authoring warning is returned for those cases, so callers cannot distinguish a minimally schema-valid element from one that lacks useful authoring guidance.
• Logs/stack trace: No runtime error or stack trace occurs; this is a missing warning in a successful validation result. TestValidateReportsAuthoringWarnings reproduces the previous behavior and verifies the warning fields and non-blocking semantics added here.

Test plan

go test ./internal/umodel -run TestValidate -count=1
go test ./internal/agentgateway -count=1
git diff --check

[qiansheng91]

Summary

Reviewed PR #98: fix(umodel): surface authoring warnings during validation

The changes appear reasonable. No critical issues found in the diff.

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Automated review by github-manager-bot

[qiansheng91]

Issue Evaluation

Category: bug | Status: Needs Verification

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Automated evaluation by github-manager-bot

[qiansheng91]

Issue Evaluation

Category: bug | Status: Under Review

Thank you for reporting this issue. It has been classified as a potential bug and is being reviewed against the current codebase.

A deeper verification will be performed. If confirmed as a valid bug, an automated fix proposal may be generated.

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Automated evaluation by github-manager

[qiansheng91]

Issue Evaluation

Category: bug | Status: Needs Info

Thank you for reporting this issue. To proceed with verification, please provide:

• Version/tag where this occurs
• Steps to reproduce
• Expected vs actual behavior
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Automated evaluation by github-manager-bot

[Chloride233]

Added the requested version, reproduction steps, expected vs. actual behavior, and verification evidence to the PR description. This is a missing warning in an otherwise successful validation result on main, so there is no runtime stack trace; the regression test captures the behavior.