v0.12.3

Fixed

• Restore MPP payments. Every --protocol mpp request failed against current MPP servers with Payment verification failed: memo is not bound to this challenge. mppx >=0.6.28 derives the TIP-20 attribution memo's trailing nonce from keccak256(challengeId) and rejects any credential whose memo does not match, while the bundled mppx 0.5.1 still filled those bytes randomly. The memo version byte did not change across that break, so servers cannot distinguish an outdated client from a replay and correctly reject both. Bumped mppx to 0.8.17 (and viem to ^2.55.16 for its peer range). x402 payments were never affected.
• Tolerate \r\n and \r line endings when framing MPP session SSE streams. Frames were split on \n\n only, so a server using CRLF framing produced no frames at all and the stream stalled silently instead of erroring.

Changed

• MPP session receipt and SSE event types are now taken from mppx's own exports instead of hand-written local copies, so an upstream shape change fails type-check rather than surfacing as a runtime payment failure.