Implement $all operator for array subset matching

[protobi-pieter]

Implemented the $all operator to check if an array value contains all elements from a constraint array.

Use Case

Select records where an array field contains all specified values. For example, finding patients who have all of diabetes (3), obesity (5), and apnea (7):

Query.query(patients, {
  conditions: {$all: [3, 5, 7]}
})

Behavior

• {x: [1,3,5,7]} with {x: {$all: [5,7]}} → TRUE (has both)
• {x: [1,3,5]} with {x: {$all: [5,7]}} → FALSE (missing 7)
• {x: []} with {x: {$all: []}} → TRUE (vacuous truth)
• Scalar values treated as single-element arrays
• Uses loose equality matching (e.g., "3" == 3)

Implementation

Follows MongoDB's $all operator semantics and the existing lhs:rhs pattern used throughout the library.

Implemented in commit 2c3936b