Adds a hand-rolled RFC 6455 WS client and minimal JSON codec to common/ (no
third-party deps, keeping legacy ForgeGradle's classpath untouched), a
DefaultBackendConnection implementing hello/hello_ack auth and reconnect
with backoff, and Forge1122ChunkAdapter deriving top-of-column state from
the vanilla heightmap for both initial chunk backfill and event-driven
deltas (block break/place, deferred one tick to read post-mutation state).
MCMapperMod wires it up with config-driven backendUrl/serverToken and a
tick-based flush batch. Verified against a live MCMapper-Backend api
instance (real WS handshake, hello_ack, and 256-column batch landing
correctly in Postgres).
common/ (shared source) plus three leaf modules: forge-1_12_2 (primary,
Enigmatica 2 target) and forge-1_7_10 both build via anatawa12's
Gradle-7-compatible ForgeGradle 1.2/2.3 forks (verified: both leaves build
clean on Gradle 7.6 / JDK 8). neoforge-26_1 is structurally scaffolded but
excluded from the default build pending its own toolchain in Phase 10.