[codex] Add Studio common events runtime

[RSamaium]

Summary

Adds the RPGJS Studio runtime side required by rpgjs/studio#29.

• Adds call_common_event and spawn_common_event runtime block schemas and executors.
• Extends the block execution context with getCommonEvent, spawnCommonEvent, and recursion state.
• Indexes commonEvents delivered by Studio map payloads.
• Uses map.createDynamicEvent(...) for non-persistent spawned common event objects.
• Updates the RPGJS Studio skill references for database, map payload, and block schema usage.

Impact

Studio-generated maps can execute hydrated common event workflows and spawn visible common event objects at runtime without extra Studio API calls.

Validation

• pnpm --dir packages/studio build -> exits 0 and generates bundles
• The build still prints existing declaration errors for package dependencies/types such as json-schema-to-ts, .ce components, and RPGJS type mismatches; these were not introduced by this change.

Companion Studio PR: rpgjs/studio#30.