Support Element#drop for files and strings

[myabc]

What

Implements Node#drop so Element#drop can drop files and strings onto an element, un-skipping the 5 Capybara Element#drop shared specs.

Why

Element#drop was force-skipped in spec/spec_helper.rb — Cuprite had no way to dispatch an HTML5 drop carrying a DataTransfer. This is the Element#drop portion deferred from #315 (HTML5 drag-and-drop).

How

Node#drop(*args) forwards to Browser#drop(node, *args), mirroring Capybara's Selenium html5_drop:

• Files (path-string args) — a hidden <input type=file> is synthesized, files are attached through Cuprite's existing select_file (CDP DOM.setFileInputFiles), then a drop is dispatched carrying DataTransfer.files.
• Strings ({type => data} args) — a DataTransfer is built via items.add/setData and a drop is dispatched.

The three JS helpers (dropString, attachDropInput, dropFile) are ported from Capybara's Selenium html5_drag.rb (DROP_STRING/ATTACH_FILE/DROP_FILE) and carry provenance comments.

Notes

• Uses only public Ferrum API — no raw CDP command() or reach-ins (per Cuprite 1.0 #307).
• Node#drop is a single-line endless method to stay within the existing Metrics/ClassLength budget on node.rb.
• Stacked on Support HTML5 drag-and-drop and drag modifier keys #315 — until that merges, this PR's diff also shows the drag-and-drop commits; it narrows to the two Element#drop commits once Support HTML5 drag-and-drop and drag modifier keys #315 lands.
• Known minor follow-up (inherited from Capybara's approach): if select_file raised mid-drop the synthesized input would not be cleaned up. Kept faithful to the upstream port for now; can harden separately.

Testing

• The 5 previously-skipped Element#drop specs (2 string + 3 file) now pass.
• Drag + drop together: 26 examples, 0 failures.
• Full suite: no new failures versus the base branch (the two #has_field validation-message failures are pre-existing — Chrome locale wording).
• bundle exec rubocop clean.

Part of #307. Follow-up to #315.

_{🤖 Authored with agent assistance.}

[Copilot]

Pull request overview

Adds HTML5 drag-and-drop support required by Capybara shared specs by (1) routing Node#drag_to through a DataTransfer-backed JS emulation when appropriate and (2) implementing Node#drop/Browser#drop so Element#drop can drop files and strings, allowing previously force-skipped Capybara specs to run.

Changes:

• Un-skips Capybara shared specs for #drag_to and Element#drop previously filtered out in spec/spec_helper.rb.
• Updates Node#drag_to to pass drop modifier keys and options through to an updated Browser#drag, with an HTML5 emulation path via lib/.../javascripts/drag.js.
• Implements Node#drop and Browser#drop, adding JS helpers in index.js to synthesize a DataTransfer for dropped strings/files.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
spec/spec_helper.rb	Removes forced skips for drag/drop shared specs so the suite exercises the new behavior.
lib/capybara/cuprite/node.rb	Adds modifier aliasing for drag and forwards new drop command to the browser.
lib/capybara/cuprite/javascripts/index.js	Adds JS helpers for drag detection and DataTransfer-backed drop for strings/files.
lib/capybara/cuprite/javascripts/drag.js	Introduces the HTML5 drag/drop emulation script (ported from Capybara Selenium).
lib/capybara/cuprite/browser.rb	Implements updated drag API + HTML5 path and new drop implementation.

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