fix(browser): inject data-fgp-ref attributes during ARIA snapshot

[twick00]

Description

Fix @eN element refs from browser.snapshot so they work with interaction methods (browser.click, browser.fill, etc.). Previously, snapshot extraction assigned @eN labels but never injected the corresponding data-fgp-ref attributes onto DOM elements, so resolve_selector("@e5") could never find them.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Refactoring
• Other (describe):

Related Issues

Element ref resolution (@eN selectors) was non-functional.

What Changed

Adds data-fgp-ref attribute injection during ARIA tree extraction on both paths:

• CDP path: Resolves BackendNodeId → NodeId via DOM.describeNode, then sets data-fgp-ref via DOM.setAttributeValue
• DOM fallback path: Injects setAttribute("data-fgp-ref", "eN") in the same JS loop that discovers interactive elements

Old data-fgp-ref attributes are cleared at the start of each snapshot to prevent stale refs from previous extractions.

Testing

• Tests pass locally (25 unit + 3 integration tests)
• Added new tests for changes
• Red/green verified: reverted the fix, confirmed tests fail (snapshot returns @e1, @e2 but 0 refs resolve to DOM elements), restored the fix, confirmed tests pass

Checklist

• Code follows project style guidelines
• Self-reviewed the code
• Commented complex logic
• Updated documentation if needed
• No breaking changes (or documented them)