fix: Improved Flexible field context detection v2 (#4)

[iamgerwin]

Summary

This PR addresses the remaining issues with Flexible field support where the dependency container was still not working correctly inside Flexible layouts.

Root Cause

The previous fix had a critical bug: when multiple NovaDependencyContainer instances exist in different Flexible groups, the first field-changed event would set the context for ALL containers, causing cross-group contamination.

Solution

Implemented a multi-method context detection approach:

1. Early Context Detection (at mount time)

• Check container's own attribute for prefix
• Check child field attributes for prefix
• Walk up Vue component tree to find Flexible layout parent
• Check DOM for input elements with prefixed names

2. Improved Event Handling

• Only cache base attribute values when the event prefix matches our context
• Filter events strictly once context is detected
• Claim context only from events that match our dependency fields

3. Prevents Cross-Group Contamination

• Each container maintains its own context
• Events from other Flexible groups are ignored

Files Changed

• resources/js/components/FormField.vue - Main improvements
• resources/js/components/DetailField.vue - Same detection improvements

Test Plan

• Verify dependency works in single Flexible layout
• Verify changing field in group 0 only affects group 0 dependencies
• Verify changing field in group 1 only affects group 1 dependencies
• Verify backward compatibility with non-Flexible fields

Related Issue

Fixes #4