fix(types): propagate Reactivity generic through RxDocument in query return types

[Copilot]

find(), findOne(), and findByIds() return RxDocument<RxDocumentType, OrmMethods> without the Reactivity generic, so doc.$$ and doc.field$$ resolve to unknown instead of the configured reactive type.

// Before: doc.age$$ is typed as `unknown`
const doc = await db.collection.findOne().exec(true);
const age: Signal<number> = doc.age$$; // TS error

// After: Reactivity propagates correctly
const age: Signal<number> = doc.age$$; // ✓

Changes

• src/rx-collection.ts — Add Reactivity as third generic to all RxDocument<RxDocumentType, OrmMethods> usages across insert, bulkInsert, bulkRemove, bulkUpsert, upsert, incrementalUpsert, find, findOne, findByIds, insertCRDT
• src/types/rx-query.d.ts — Propagate OrmMethods and Reactivity in all query chaining method return types (equals, eq, or, gt, regex, etc.)
• src/rx-query.ts — Propagate generics through where, sort, skip, limit, asRxQuery, tunnelQueryCache
• test/typings.test.ts — Add compile-time type tests for Reactivity propagation through findOne().exec(), find().exec(), findByIds().exec(), and query chaining