v0.1.0-alpha.8: dive and drowning acceptance adapter

Adds the dive protocol scenario and LyraCore acceptance adapter. It sends typed swimming movement, verifies the Breath timer, waits through the advertised window, and requires an own Character Drowning log whose damage matches the observed health drop. Surfacing must stop the Breath timer before logout.

The adapter verifies the imported liquid cell before changing a clearly named disposable Character. Credentials enter through stdin. Invalid identity, coordinates, database names, and unsuitable terrain stop before Character changes.

PR #10 passed parent review, 75 tests, strict clippy, release builds, offline adapter checks, ShellCheck, and Ubuntu/macOS/coverage CI. Coordinate selection, live Realm execution, head-height calibration, and stock-client acceptance remain with the Operator.