MappedItemRegistry

Accumulates Geyser definition entries across the generic Java→Bedrock pipeline. One instance per BedrockConversion.generate call.

Deduplication rules:

• registerModelOnce returns true exactly once per unique bedrockSafeIdentifier — the orchestrator must write geometry/texture files only on the first call.
• addMapping first dedupes by the tuple (baseItem, bedrockIdentifier, predicateShape) — two leaves under the same base item that resolve to the same model with the same predicate stack are skipped silently (Geyser rejects duplicate identifiers outright).
• It then dedupes by Geyser's conflict identity (base item + emitted model + parsed predicate set). Geyser registers only one definition per identity and logs "both entries have the same predicates" for the rest, so emitting both would just pick a random winner at boot. Sources of such pairs: two merged packs claiming the same custom_model_data on one item with different models, duplicate thresholds/overrides inside a single pack, and dual-format packs whose modern items definition and legacy override describe the same matcher. Winner policy: a modern type=definition entry beats a type=legacy one (modern is what current Java clients render); between entries of the same type the last one wins, matching vanilla's pick among duplicate thresholds/overrides. Dropped pairs are reported via dedupNotes for the caller's one-line summary.

The safeIdentifier rule matches Rainbow's Rainbow.bedrockSafeIdentifier (Rainbow.java:18-20): ':' ->'.', '/' ->'_'. Used for filesystem paths and the item_texture.json lookup key.