refactor: expose Query::shape() as iterative instance method

[lohanidamodar]

Follow-up to #3 — per @abnegate's review comment:

If we need an instance anyway, lets make it an instance method shape, with a loop instead of recursion.

Changes

• Extract the canonical-shape helper out of fingerprint() and into a public instance method Query::shape().
• Replace the recursive walk with an iterative post-order traversal: preorder-flatten the tree via a stack, then process the reversed list so every node's children are shaped before the node itself.
• fingerprint() now just calls $query->shape() on each element.

API

Query::equal('name', ['Alice'])->shape();
// => 'equal:name'

$and = new Query(Query::TYPE_AND, '', [
    Query::equal('name', ['Alice']),
    Query::greaterThan('age', 18),
]);
$and->shape();
// => 'and:(equal:name|greaterThan:age)'

Test plan

Added testShape() covering leaf, logical, elemMatch, and 4-level-deep nested queries. Confirms iterative output matches the recursive baseline and that elemMatch's attribute is preserved in its shape.

Mirrors the same refactor applied to utopia-php/database#859.

[greptile-apps]

Greptile Summary

This PR extracts a canonical shape computation from fingerprint() into a public instance method Query::shape(), replacing the prior recursive walk with an iterative preorder-flatten + reversed-pass approach. The algorithm is correct: parents are always emitted before their children in the preorder list, so after reversing, every node's children are guaranteed to have their shapes resolved before the node itself is processed. The spl_object_id keying is safe because $nodes holds strong references to every object throughout the traversal.

Confidence Score: 5/5

Safe to merge — no correctness, security, or data-integrity issues found.

All findings are P2 or lower. The core invariant (children resolved before parents in the reversed list) holds by construction of a preorder traversal, and tests cover leaf, logical, elemMatch, and 4-level-deep nesting.

No files require special attention.

Important Files Changed

Filename	Overview
src/Query/Query.php	Adds public iterative shape() method and updates fingerprint() to delegate to it; traversal logic is algorithmically correct.
tests/Query/QueryTest.php	Adds testShape() covering leaf, logical, elemMatch, and 4-level-deep nested queries; all assertions match the algorithm's output.

_{Reviews (1): Last reviewed commit: "refactor: expose shape() as an iterative..." | Re-trigger Greptile}