[log] middleware: add debug logging calls to jqschema (#4912)

## Summary

Adds `logMiddleware.Printf` debug logging calls to
`internal/middleware/jqschema.go`.

The `logMiddleware` logger was declared (`var logMiddleware =
logger.New("middleware:jqschema")`) but never used. This PR activates it
with 4 meaningful logging calls:

### Changes

- **`WrapToolHandler`** – logs when a tool handler is wrapped with the
middleware, including `toolName`, `sizeThreshold`, `baseDir`, and
whether a `pathPrefix` is set
- **`applyJqSchema`** (entry) – logs the start of schema inference with
the Go type of the input data
- **`applyJqSchema`** (exit) – logs successful schema inference with the
result type
- **`ShouldApplyMiddleware`** – logs the apply/skip decision for each
tool

### Why this matters

The existing operational logging uses `logger.LogInfo/LogDebug` (written
to files). The `logMiddleware` calls provide developer-facing trace
output enabled only when `DEBUG=middleware:*` is set, following the
pattern used throughout the codebase.

### Testing

- All unit tests pass: `go test ./internal/middleware/...`
- No new imports required (logger package already imported)
- No side effects in log arguments




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Author: lpcox

internal/middleware/jqschema.go

@@ -172,6 +172,8 @@ func applyJqSchema(ctx context.Context, jsonData interface{}) (interface{}, erro
 		return nil, fmt.Errorf("jq schema filter not compiled (check startup logs): %w", jqSchemaCompileErr)
 	}
 
+	logMiddleware.Printf("applyJqSchema: starting schema inference, dataType=%T", jsonData)
+
 	// Ensure context has a timeout - add default if none exists
 	if _, hasDeadline := ctx.Deadline(); !hasDeadline {
 		var cancel context.CancelFunc
@@ -212,6 +214,7 @@ func applyJqSchema(ctx context.Context, jsonData interface{}) (interface{}, erro
 	}
 
 	// Return the schema object directly (no JSON marshaling needed here)
+	logMiddleware.Printf("applyJqSchema: schema inference completed, resultType=%T", v)
 	return v, nil
 }
 
@@ -288,6 +291,8 @@ func WrapToolHandler(
 	sizeThreshold int,
 	getSessionID func(context.Context) string,
 ) func(context.Context, *sdk.CallToolRequest, interface{}) (*sdk.CallToolResult, interface{}, error) {
+	logMiddleware.Printf("WrapToolHandler: wrapping tool=%s, sizeThreshold=%d bytes, baseDir=%s, pathPrefixSet=%v",
+		toolName, sizeThreshold, baseDir, pathPrefix != "")
 	return func(ctx context.Context, req *sdk.CallToolRequest, args interface{}) (*sdk.CallToolResult, interface{}, error) {
 		// Generate random query ID
 		queryID := generateRandomID()
@@ -475,5 +480,7 @@ func WrapToolHandler(
 // Currently applies to all tools, but can be configured to filter specific tools
 func ShouldApplyMiddleware(toolName string) bool {
 	// Apply to all tools except sys tools
-	return !strings.HasPrefix(toolName, "sys___")
+	applies := !strings.HasPrefix(toolName, "sys___")
+	logMiddleware.Printf("ShouldApplyMiddleware: tool=%s, applies=%v", toolName, applies)
+	return applies
 }