MONGOID-5759 ensure unpersisted documents are picked up via HasMany#find

[jamis]

When using find with a block on a has-many association, Mongoid does not include unpersisted documents in the search. This PR fixes that bug.

[Copilot]

Pull request overview

Fixes HasMany#find with a block so that it searches in-memory (built/unpersisted) associated documents in addition to persisted records, addressing MONGOID-5759.

Changes:

• Add specs verifying has_many #find { ... } returns built/unpersisted documents when the parent is not persisted.
• Update HasMany::Proxy#find to use in-memory enumeration (detect) when called with only a block.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
spec/mongoid/association/referenced/has_many/proxy_spec.rb	Adds regression coverage for #find with block to include built/unpersisted documents when parent is new.
lib/mongoid/association/referenced/has_many/proxy.rb	Adjusts #find behavior for block-only calls to search the association enumerable (including _added docs).

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[Copilot]

Proxy#find handles the common find { ... } case by calling detect, which makes built/unpersisted documents visible. However, Mongoid::Criteria#find (and Ruby's Enumerable#find) also support the optional ifnone Proc argument (find(-> { default }) { ... }). With the current condition (block_given? && args.empty?), that form still delegates to criteria.find and will continue to ignore built/unpersisted documents. Consider matching the same empty_or_proc logic as Mongoid::Findable#find / Criteria#find and calling detect(*args, &block) when a block is given and args are empty or a single Proc.