0.6.1 - Tracks Hearth 0.4.1 and its compile-time performance lessons

A maintenance release on top of the 0.6.0 rebuild. There are no API changes — pipez tracks the freshly released Hearth 0.4.1 and applies its compile-time-performance lessons to the derivation layer. If you are on 0.6.0, this is a drop-in bump (MiMa is enabled against 0.6.0 and green).

• bump the Hearth dependency to 0.4.1 and enable MiMa against 0.6.0
• apply Hearth's 0.4.1-line macro-compilation lessons: defer namedScope prettyPrint, use unsortedMethods, filter-first method getters, and cheaper collection idioms in codegen
• pick up the Hearth enum-order determinism fix (stable declaration order for sealed-hierarchy children)
• docs: mention Hearth as the macro toolkit pipez is built on; fix repository organization links