Decide semantics for multi-key expressions

[mutaimwiti]

Object.entries(exp)[0] silently truncates { $and: […], $or: […] } to the first key. Either adopt MongoDB's implicit-AND across keys or throw a clear error. Pick before v1.0. (Discussion, no version target.)

[mutaimwiti]

Decision: adopt MongoDB-style implicit-AND across keys, so { $and: [...], $or: [...] } evaluates as ($and) AND ($or), rather than throwing.

Rationale: it's a natural extension of the model, and the existing stepAll AND-walker already gives us sync/async handling and short-circuit for free, so the implementation is small.

Deferring the implementation to a follow-up PR before v1.0. Leaving this issue open to track that work.

[mutaimwiti]

Update: this shipped sooner than the earlier comment suggested. Implicit-AND across keys (at any nesting depth) was implemented in #12 and released in v0.3.0, rather than a separate follow-up. An empty object {} now throws a LogicalCompilerError (EXPECTED_EXPRESSION) instead of a raw TypeError. Closed via #12.