The pen P0 work added a new embeddable C entry point (punktfunk_connection_send_pen)
but left ABI_VERSION at 12 — the value 0.18.0 shipped. Per the project's convention
(0.18.0 bumped to 12 for the additive cursor channel), additive C-surface growth bumps
the ABI so embedders can gate on the new symbol. Regenerated include/punktfunk_core.h
via cbindgen (cargo build -p punktfunk-core); WIRE_VERSION is unchanged (pen is
capability-gated on HOST_CAP_PEN).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 4.8
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