fix(chat): keep evidence.go out of the tool consumer matrix

The comment in sourceURLs named ExecuteMCPToolCall, which the tool
consumer matrix test (core/services/addons/tools) reads as a marker of a
file that discovers or executes tools. evidence.go only reads tool
output, so reword the comment instead of classifying the file.

Docs-Not-Needed: comment-only change, no behaviour change
Assisted-by: Claude Code:claude-opus-5-5
Signed-off-by: Stefan Walcz <stefan.walcz@walcz.de>

core/http/endpoints/openai/evidence.go

@@ -28,7 +28,7 @@ func sourceURLs(texts []string) []string {
 	var urls []string
 	seen := map[string]struct{}{}
 	for _, text := range texts {
-		// ExecuteMCPToolCall JSON-encodes multiple TextContent results.
+		// The MCP tool call path JSON-encodes multiple TextContent results.
 		// Decode that envelope so escaped query separators remain intact.
 		var parts []string
 		var single string