Serve common/echo.py as HTML with byte-preserving first query values, all-method handling, and ordered response pipes. Recognize exact relative and absolute references during case discovery.
Validation: 582 Python tests passed with 32 workers; 144 HTTP responses matched official wptserve for status, body, and 15 response fields. New regression tests fail on the unmodified main baseline.
Source-commit: 4042e1a11a
