fix: validate inference history is valid json

[mattjohnsonpint]

Fixes #903

[Copilot]

Pull Request Overview

This PR adds JSON validation for inference history entries to ensure only valid JSON is stored, adjusts database logging to mark certain errors as user-visible, and documents the change in the changelog.

• Add gjson validation and error handling in getInferenceDataJson
• Update logDbWarningOrError to include a user_visible flag on logged errors
• Record the fix in CHANGELOG.md

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
runtime/db/inferencehistory.go	Renamed local variable, added gjson.ValidBytes check, and return error on invalid JSON
runtime/db/db.go	Modified logger call to include user_visible metadata
CHANGELOG.md	Added entry for v0.18.2 with JSON validation fix

Comments suppressed due to low confidence (2)

runtime/db/inferencehistory.go:181

• Consider adding unit tests to cover both valid and invalid JSON inputs so the new validation logic is exercised and guarded against regressions.

	if !gjson.ValidBytes(result) {

runtime/db/inferencehistory.go:22

• The code uses fmt.Errorf on line 182 but fmt is not imported; add import "fmt" to avoid a compilation error.

	"github.com/tidwall/gjson"