fix: single-column BTree index Range filter/delete

[DexterKoelson]

Fixes #4736

Description of Changes

Single-column BTree indexes accepted Range<T> in their type signatures (via IndexScanRangeBounds), but the runtime filter() and delete() implementations always serialized the argument as a point value using datastore_index_scan_point_bsatn. Passing a Range object caused SyntaxError: Cannot convert [object Object] to a BigInt because the Range object was fed directly to the column serializer.

The fix adds Range detection to the single-column BTree index code path in runtime.ts. When a Range is passed, it serializes the bounds and calls datastore_index_scan_range_bsatn / datastore_delete_by_index_scan_range_bsatn instead. Point queries continue to use the existing fast path. The multi-column index code already handled Range correctly — this brings single-column indexes to parity.

API and ABI breaking changes

None. This is a pure bugfix. Existing queries are unaffected, and Range queries that previously crashed now work as the types imply.

Expected complexity level and risk

Low. The change is localized to one code path in runtime.ts and mirrors the existing multi-column range serialization logic. All 170 existing tests pass.

Testing

• All 170 vitest tests pass
• Manually confirmed the fix resolves the reported SyntaxError in a production SpacetimeDB TypeScript module using ctx.db.players.fooId.filter(new Range(...)) on a single-column BTree index