refactor(knowledge): extract generic CUE compiler core and projection…

[ljahier]

… seams

[mendral-app]

Needs attention — 1 issue in 1 file

The path-traversal vulnerability in sourceProvenance (runtime.go:480) flagged in the previous review remains unfixed — project.Package is joined to root and passed to WalkDir without the ..-escape guard that packageInstance in evaluator.go:629-641 implements. The rest of the new code is well-structured with good test coverage, consistent error handling, and appropriate bounds on the query API.

What this PR does

Extracts a generic CUE compiler core and transport-independent knowledge runtime with catalog, query, evaluation, and provenance APIs. Adds an optional CUE metadata contract (cue/knowledge/knowledge.cue), bounded query API with catalog validation, and named evaluation execution with JSON input overlays. The CLI health check is routed through the new runtime. All new files carry MPL-2.0 headers.

Prompt for AI agents (all issues)

Check if these issues are valid — if so, understand the root cause of each and fix them.

<assessment>
The path-traversal vulnerability in `sourceProvenance` (runtime.go:480) flagged in the previous review remains unfixed — `project.Package` is joined to root and passed to `WalkDir` without the `..`-escape guard that `packageInstance` in evaluator.go:629-641 implements. The rest of the new code is well-structured with good test coverage, consistent error handling, and appropriate bounds on the query API.
</assessment>

<file name="backend/internal/knowledge/runtime.go">
<issue location="backend/internal/knowledge/runtime.go:478">
`sourceProvenance` still joins `project.Package` to root without the `..`-escape check that `packageInstance` in `evaluator.go:629-641` carefully implements. A crafted `Package` value (e.g. `../../etc`) causes `WalkDir` to read arbitrary directories outside the module root. This was flagged in the previous review and remains unfixed.
</issue>
</file>

_{Tag @mendral-app with feedback or questions. View session}

[mendral-app]

security (P1): sourceProvenance still joins project.Package to root without the ..-escape check that packageInstance in evaluator.go:629-641 carefully implements. A crafted Package value (e.g. ../../etc) causes WalkDir to read arbitrary directories outside the module root. This was flagged in the previous review and remains unfixed.

Suggested change

Suggested change

	packageDir := root
	if project.Package != "" && project.Package != "." {
	packageDir = filepath.Join(root, project.Package)
	}
	packageDir := root
	if project.Package != "" && project.Package != "." {
	if filepath.IsAbs(project.Package) {
	return Provenance{}, fmt.Errorf("package must be a relative path")
	}
	packageDir = filepath.Join(root, project.Package)
	rel, err := filepath.Rel(root, packageDir)
	if err != nil || rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) {
	return Provenance{}, fmt.Errorf("package path escapes module root")
	}
	}

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At backend/internal/knowledge/runtime.go, line 478:

<issue>
`sourceProvenance` still joins `project.Package` to root without the `..`-escape check that `packageInstance` in `evaluator.go:629-641` carefully implements. A crafted `Package` value (e.g. `../../etc`) causes `WalkDir` to read arbitrary directories outside the module root. This was flagged in the previous review and remains unfixed.
</issue>